Fluid Stepper Motor

Abstract

A stepper motor of the type in which fluidic logic cooperates with a fluidic actuator to produce a rapid high torque positional displacement of the actuator's output member, the fluidic logic in response to an input command to change the position of the actuator's output member from a first position to second position generates a sequential set of coded signals operative to stepwise drive the output member of the actuator in either direction until the logic generates a coded signal corresponding to the position commanded by the input.

Description

BACKGROUND OF THE INVENTION

The use of stepping motors in positioning control systems is well known in the prior art. The bulk of the prior art uses electro-mechanical position control systems with electrically driven stepper motors. However, various types of fluid stepping motors have been developed in the past to perform specific functions. One type of fluidic stepping motor converts the substantially constant rotary output motion of a fluid motor into intermittent rotary output motion by means of fluidic actuated pawls engaging a ratchet wheel attached to the output member of the fluid motor. This type of fluidic stepping motor is described in U.S. Pat. No. 3,616,979. Another type of fluidic stepping motor is discussed in U.S. Pat. No. 2,978,889 in which a number of fluid driven pistons sequentially drive a ratchet wheel. The pistons are systematically actuated so that the output member attached to the ratchet wheel driven through a precise angle. Another type of fluid operated stepper motor is described in U.S. Pat. No. 3,411,413 in which a vane in a closed chamber is caused to step from one position to another by applying fluidic pressure to one side of the vane and venting the other side. The vane rotates to the desired position where the pressure on both sides of the vane are equalized. Another type of system is illustrated by the fluidic numerical communicator described in U.S. Pat. No. 3,561,676. The system incorporates a fluid driven rotatable member having a face with a plurality of coded slots which when sensed provide a coded fluidic signal indicative of the position of the rotating member. These coded signals from the sensors are communicated to a comparator which compares these coded signals with the input command and generates a signal when the coded signal and the command are identical. The generated signal activates a pawl which stops the rotating member in the desired position. This device is capable of translating the given input signal into a predeterminable mechanical position. A more sophisticated type of positioning control system is illustrated in U.S. Pat. No. 3,606,817. The positioning control system compares the actual position of the mechanically driven device with the input command and drives the device to the position indicated by the input command. The position of the driven device is determined by a set of transducers which produce a coded signal indicative of the existing position of the driven device. This signal is compared with the input command in a comparator which generates a signal to drive a fluidic motor until the output position agrees with the input command.

For the most part, the stepper motors found in the prior art require sensors to determine the position of the output member and are not capable of producing high output torques. This inability to generate high output torques is also found in the electro-mechanical stepper motors wherein the stepper motors are electrically activated. The object of this invention is to provide a stepper motor which overcomes many of the problems of the prior art devices. This motor is capable of producing a high output torque with accurate positional displacements and can be applied to machine tools for accurate and rapid positioning of the workpiece without employing feedback sensors. Beside positioning applications, this stepper motor finds use in indexing, counting, cutting, and many other standard control needs. The use of fluidic logic provides for easy interfacing with fully automatic systems.

SUMMARY OF THE INVENTION

The invention is a fluid actuator driven by fluidic logic to form a stepper motor with a high output torque and accurate positional displacements. The fluidic logic generates a sequential set of coded signals which drive the output members of the fluid actuator in sequential steps of equal magnitude in a predeterminable direction. Each coded signal generated by the fluidic logic corresponds to a predeterminable position of the output member of the fluidic actuator, and each sequential coded signal corresponds to the sequential position of the output member. In addition to generating the sequential sets of coded signal, the logic generates a decoded signal which corresponds to both the generated coded signal and the position of the output member of the fluid actuator. This decoded signal is used in conjunction with a step selector to cause the stepper motor to sequentially step to a desired step or position, in response to an input command to the step selector. The fluid actuator is of the rotary type in which a ring element is orbited within a stationary reaction chamber about an output member. The ring element is orbited by a force vector generated by the fluidic signals received from the fluidic logic. This force vector is indexed about the circumference of the ring element in equal angular increments by the sequential set of fluidic signals generated by the fluidic logic. The orbiting member drives the output member through angular increments proportional to the angular displacement of the orbiting member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the basic elements of the stepper motor.

FIG. 2 is a sectional side view of the fluid actuator.

FIG. 3 is a sectional front view of the fluid actuator.

FIG. 4 is an enlarged view of a section of FIG. 3.

FIG. 5 is a fluidic schematic showing the details of a preferred embodiment of the fluidic clock.

FIG. 6 is a fluidic schematic showing the details of a preferred embodiment of the phase generator.

FIG. 7 is the symbol for a fluidic bistable flip flop element.

FIG. 8 is a table giving the sequence of coded signals generated by the phase generator, at the output terminals A, B and C.

FIG. 9 is a fluidic schematic showing the details of a preferred embodiment of the code generator, decoder and the step selector switch.

FIG. 10 is a table illustrating the sequence of the 9 sets of coded signals generated by the code generator at the output terminals V.sub.1 through V.sub.9.

FIG. 11 is a fluidic schematic showing the details of a preferred embodiment of the interface and the fluid actuator.

FIG. 12 is a fluidic schematic showing the details of a preferred embodiment of the step selector and inverter amplifier.

FIG. 13 is a fluidic diagram of the direction selector.

FIG. 14 is a fluidic diagram of the reset switch.

The essential elements of the stepper motor are shown in the block diagram of FIG. 1 in which the Stepper Motor 10 consists of Fluidic Logic 11 generating a repetitive set of sequentially coded signals which drive the Output Member 13 of a Fluidic Actuator 12 in a stepwise manner to a predeterminable position. The functional operation of the Stepper Motor 10 is controlled by input commands to the Fluidic Logic 11. The embodiment illustrated in FIG. 1 shows a stepper motor provided with six inputs to the Fluidic Logic 11 which may be manual inputs from a human operator or may be programmed inputs from a control device not shown. The Step Selector 14 is a position control corresponding to the desired position of the Output Member 13 of the Fluidic Actuator 12. Movement of the Step Selector to a desired position causes the Fluidic Logic 11 to generate sequential sets of coded signals which drive the fluid actuator Output Member 13 to the selected position. When the set of signals generated by the Fluid Logic corresponds to the selected position, an inhibit signal is generated which stops the Fluid Logic from generating the next sequential set of signals. Activation of the Cycle Selector 15 directs the Fluidic Logic 11 to generate one complete cycle of sequentially coded signals. The response of the Fluidic Actuator 12 to one complete cycle of coded signals may correspond to one full revolution of the Output Member 13, or may be some multiple or submultiple thereof as will be discussed later with reference to the Fluidic Actuator 12. The Mode Selector 16 has two positions, the "run" position which terminates the response of the Fluidic Logic 11 to the inhibit signal of the Step Selector 14, and the "step" position in which the operation of the fluidic logic is controlled by the signal from the Step Selector 14. The Direction Selector 17 is illustrated as having three input positions, the "Hold" position prevents the operation of the Fluidic Logic 11 irrespective of the input commands to the Step Selector 14, Cycle Selector 15 or Mode Selector 16; the "Clockwise" (CW) position operative to cause the Fluidic Logic 11 to generate a repetitive set of sequentially coded signals which drive the Output Member 13 of the Fluidic Actuator 12 in one direction; and the "Counter Clockwise" (CCW) position operative to drive the Output Member 13 in the opposite direction. The Rate Control 18 controls the frequency or rate at which the sequential coded signals are generated by the fluid logic.

The Clock 19 is a variable frequency fluidic oscillator which generates a mirrored pair of output signals. The frequency of the output signals generated by the clock is controlled by the Rate Control 18. The "on-off" function of the clock is controlled by the inhibit signal generated by the Position Selector 14. The receipt of an inhibit signal will cause the clock to stop.

The phase Generator 20 responds to the signals from the Clock 19 and generates a repetitive set of sequential phase coded signals. The Code Generator 21 responds to the phase coded signals generated by Phase Generator 20 and generates a repetitive set of sequential position coded signals corresponding to the signals required by the Fluidic Actuator 12 to drive the Output Member 13 to a predeterminable position. The output signals of the Code Generator 21 are sequentially coded so that the successive sets of coded signals correspond to the signals required to move Output Member 13 of the actuator one step at a time in the desired direction. Each successive signal drives the Output Member 13 one more step in the desired direction.

The Code Generator 21 is also controlled by the signals from the Direction Selector 17. A "clockwise" signal generated by the Direction Selector 17 causes the Code Generator 21 to generate a set of signals which will sequentially step the output of the actuator in one direction, a counter clockwise signal received from the Direction Selector 17 will cause the code generator to generate a set of signals which will sequentially step the output of the actuator in the opposite direction.

The Interface 22 amplifies the position coded signals generated by the Code Generator 21 and transmits the amplified signals to the Fluidic Actuator 12 increasing the fluidic power driving the actuator. The position coded signals from the Code Generator 21 are also communicated to the Decoder 23 which generates a decoded signal corresponding to the position coded signals being transmitted to the fluid actuator. The decoded signal is transmitted to the Step Selector 14 which responds to the selected decoded signal and generates an inhibit signal when the decoded signal is indicative of the position selected by the input command. The Position Indicator 24 also responds to the signals generated by the code generator and generates a visual indication of the position of the actuator output as represented by the coded signals.

The Reset 25 is an auxiliary control which resets the Phase Generator 20 and the Code Generator 21 so that their outputs are predeterminable coded signals. These predeterminable coded signals may correspond to the first signal of the repetitive set of coded signals generated by the respective generators or may be signals which correspond to any other predeterminable position of the Actuator Output Member 13.

The Fluid Actuator 12 is illustrated in FIGS. 2 and 3 as a rotary actuator of the type in which a ring member is orbited within a stationary reaction member and about an output member. The ring member is driven to orbit the output member by the force vector generated by the set of fluidic signals received from the Fluidic Logic 11. The force vector is indexed about the circumference of the ring member by the sequential signals from the fluidic logic causing the ring member to orbit the output member causing the output member to rotate. The Fluid Actuator 12 has a Housing 26 with an Integral Stationary Gear 27 forming a Chamber 28 within the Housing 26. A ring member shown as a Ring Gear 29 and an output member shown as the Output Gear 30 are internally contained within the Chamber 28 by the Front Plate 31 and Rear Plate 32 of the Housing 26. The Output Member 13 of the Fluidic Actuator 12 is shaft eccentrically attached to the Output Gear 30. The Output Member 13 is rotatably attached to the Front Plate 31 and Rear Plate 32 of the Housing 26 by Bearing Means 33 and 34 secured respectively to the Front Plate 31 and Rear Plate 32 so that the rotational axis of the Output Member 13 is concentric with the Chamber 28. The Ring Gear 29 has an external set of Teeth 35 equal in number to the number of teeth on the Stationary Gear 27 and are configured to mate therewith. The effective external diameter of the Ring Gear 29 is less than the effective diameter of the Stationary Gear 27 so that the Ring Gear is free to move laterally or orbit inside the stationary gear, but not rotate within the Chamber 28. The Ring Gear 29 also has an internal set of Teeth 36 configured to mate with the teeth of the Output Gear 30. This type of fluidic actuator is sufficiently known in the art, that a detailed description of its operation is not required. It is sufficient to state that the orbiting of the ring gear within the confines of the stationary gear will cause the output gear to rotate in a direction opposite to the orbital rotation of the ring gear at a rate which is proportional to the difference in the number of mating teeth on the Output Gear 30 and the Ring Gear 29. The Displacement Chamber 37 between the Stationary Gear 27 and the Ring Gear 29 is subdivided isolated Compartments 38 by Vanes 39 as shown in the enlarged section of the fluid actuator illustrated in FIG. 4. Each Compartment 38 is capable of being individually pressurized through an associated Inlet 40 through the Rear Plate 32 of the Housing 26. The Ring Gear 29 has Fluid Passages 41 which communicate between the individual Inlets 40 and the associated Compartment 38. Pressurizing a set of adjacent compartments will generate a force vector operative to move the ring gear in a radial direction away from the pressurized compartments. This force vector may be caused to rotate by pressurizing an adjacent compartment at one end of the set of pressurized compartments and venting to air the last pressurized compartment at the opposite end of the pressurized set. The adding of one pressurized compartment while venting another at the opposite end of the previous pressurized set causes the force vector to rotate through an angle equal to the angular size of each compartment. Rotation of the force vector also causes the ring gear to orbit through an equal angle.

The embodiment illustrated in FIG. 3 has the displacement chamber divided into 9 compartments of equal angular size, however, the number of compartments in equally operative devices may be more or less. Referring to the illustrated 9 compartment fluidic actuator, a high force vector is generated when 4 adjacent compartments are pressurized and the remaining 5 are vented to air. This force vector can be rotated through one revolution in nine equal steps by pressuring an adjacent chamber and venting the one at the opposite end of the pressurized set as discussed above. This sequence establishes the code shown in FIG. 10 which lists the chambers which are to be pressurized for a desired position of the Ring Gear 27. It is recognized that other codes can be generated which will produce operative force vectors.

The fluidic logic is operative to generate the illustrated code in the sequence shown so that the Output Member 13 of the fluid actuator will rotate through a precise angle for each sequential coded signal generated by the fluid logic.

The speed or the frequency at which the coded signals are generated by the fluidic logic is controlled by the fluidic clock. The output signal of an active Fluidic Amplifier 51 illustrated as an OR/NOR amplifier in FIG. 5 is fed back to one of the inputs of the amplifier by means of the Constriction 52 and the Fluidic Capacitor 53. The Constriction 52 and Capacitor 53 cooperate to delay the signal generated at the output of the Fluidic Amplifier 51 before it is capable of activating the input and terminating the output signal. This closed fluidic loop oscillates at a predeterminable frequency controlled by the fluidic properties of the Fluidic Amplifier 51, the Constriction 52 and the Fluidic Capacitor 53. The OR output signal from the amplifier is transmitted to an input of a second Fluidic Amplifier 54, also illustrated as an OR/NOR fluidic amplifier where this signal is amplifieed producing alternating OR and NOR signals. An inhibit signal generated by the Step Selector 14, communicated to the alternate gate of the Amplifier 54, will lock Amplifier 54 in the OR signal generating state and termiante the response of this amplifier to the signals generated by Amplifier 51.

The frequency of the oscillator comprising Amplifier 51, Constriction 52, and Capacitor 53 may be made variable by providing a bias signal at the input gate of Amplifier 51. This bias signal is controlled by Valve 55 bleeding a measured quantity of fluid from the Pressure Source 50 to the input of the Amplifier 51 establishing a bias pressure at the input gate. Increasing the bias signal reduces the feedback signal required to make the amplifier switch states, therefore, the Amplifier 51 will oscillate at a faster rate. Decreasing the bias signal increases the signal required to make the amplifier switch states and causes the amplifier to oscillate at a slower rate.

The OR and NOR signals from Amplifier 54 are transmitted to the Phase Generator 20 illustrated in FIG. 6. The illustrated embodiment of the phase generator comprises six fluidic amplifiers designated as 61 through 66 and six bistable fluidic elements designated as 71 through 76, in a cyclic feedback arrangement to form a repetitive shift register. The illustrated embodiment uses NOR fluidic amplifier and bistable fluidic amplifiers, however, it is recognized that other types of active fluidic elements may be used to perform comparable functions. A typical bistable element illustrated in FIG. 7 has a set gate C.sub.1, a clear gate C.sub.2, and a reset gate R. It also has a set output 01 and clear output 02. A fluid signal at the set gate C.sub.1, causes the bistable element to generate a signal at the set output 01, and terminates a signal at the clear output 02. A signal at the clear gate C.sub.2 causes the bistable element to change state generating a signal at the clear output 02 and terminating the signal at the set output 01. A reset R input places the bistable element in either the set or clear state according to whether reset is operable to function as a set or clear input gate.

In operation, the OR signal from the Clock 19 is transmitted to the Amplifiers 61, 63 and 65, and the NOR signals are transmitted to Amplifiers 62, 64 and 66. The output signal of Amplifier 61 is transmitted to the set gate of Bistable Element 72 and the clear gate of Bistable Element 71. The clear output of Bistable Element 71 is transmitted back to the alternate input gate of Amplifier 61. In a similar manner the output of Amplifier 62 is transmitted to the set gate of Bistable Element 73 and the clear gate of Bistable Element 72 and the clear output of Bistable Element 72 is transmitted to the alternate input gate of Amplifier 62. The remaining amplifier and bistable elements are connected in a like manner, with the output of Amplifier 66 transmitting signals to the clear gate of Bistable Element 76 and the set gate of Bistable Element 71 making the fluidic circuit cyclic so that the output signals will be repetitive.

The states of the Bistable Elements 71 through 76 may initially set by a reset signal from the Reset Control 25 so that the clear outputs from all the bistable elements are in the ONE state except the clear output of Bistable Element 71 which is in the ZERO state. In this description, the ONE state represents a positive fluidic signal and the ZERO state represents a signal of lesser amplitude or no fluidic signal. The feedback signals from the bistable elements to the inputs of their associated amplifiers are then ONE for all amplifiers except Amplifier 61 which has a ZERO signal feedback signal. The Clock 19 is normally stopped by an inhibit signal from either the Direction Selector 17 or the Step Selector 14, therefore, the OR signals transmitted from the clock to Amplifiers 61, 63 and 65 are ONE's and the NOR signal communicated to Amplifiers 62, 64 and 66 are ZERO's. The clock signals in the inhibited state do not cause any changes in the reset state of the phase generator. The first clock signal inverts the signals to the amplifiers so that Amplifiers 61, 63 and 65 now receive ZERO signals, and Amplifiers 62, 64 and 66 now receive ONE signals. Amplifier 61 is the only amplifier which has ZERO inputs at both of its input gates and therefore the only amplifier which will generate an output signal. The output signal of Amplifier 61 is communicated to the clear gate of Bistable Element 71 and the set gate of Bistable Element 72. Bistable Element 71 clears and feeds back a ONE signal to the input gate of Amplifier 61. Bistable Element 72 sets and transmits a ZERO signal to terminal designated A and also feeds back a ZERO signal to the input of Amplifier 62. The states of the remaining elements of the phase generator remain unchanged. The next signal from the clock is inverted again, and transmits ONE signals to Amplifiers 61, 63 and 65 which do not cause these amplifiers to produce an output signal and ZERO signals to Amplifiers 62, 64 and 66. Amplifier 62 is now capable of generating an output signal because it has ZERO signals at both inputs. The output signal of Amplifier 62 clears Bistable Element 72 which feeds back a ONE signal to the input of Amplifier 62 and restores A to a ONE and sets Bistable Element 73 which feeds back a ZERO signal to the input of Amplifier 63. The next signal from the clock in a similar manner causes Amplifier 63 to generate an output signal which clears Bistable Element 73 feeding back a ONE signal to Amplifier 63 and sets Bistable Element 74 generating a ZERO signal at Terminal B of the phase generator and also feeds back a ZERO signal to the input of Amplifier 64. One skilled in the art will readily see that for subsequent signals from the clock, the ZERO output signal will shift to the next successive bistable element. The output signal of the phase generator is taken from the clear outputs of Bistable Elements 72, 74 and 76 designated as A, B and C. The output signals generated by each successive clock cycle is given in the code table of FIG. 8.

The coded output signals from the Phase Generator 20 are transmitted to the Code Generator 21 illustrated in FIG. 9. The illustrated embodiment of the code generator comprises nine (9) NOR fluidic amplifiers designated as 101 through 109, for generating a counter clockwise code, nine (9) NOR fluidic amplifiers designated as 111 through 119 for generating a clockwise code and nine (9) bistable fluidic elements designated as 121 through 129 cooperating with both sets of fluidic amplifiers to produce the desired sequential code. The Direction Selector 17 applies fluidic power to one or the other set of amplifiers, rendering the alternate set inoperative.

The coded output signal of the Code Generator 21 is generated at the set output of the bistable elements designated as V.sub.1 through V.sub.9. Each bistable element has a reset input which upon a reset command establishes the output code shown as Line 1 on the Code Table illustrated in FIG. 10. The reset position is illustrated as Position 1, however, it may be any other position that has a more meaningful function when the stepper motor is used in combination with another device.

In operation, the coded output signals from the phase generator are transmitted to both sets of NOR Amplifiers 101 through 109 and 111 through 119 as illustrated in FIG. 9. The output signal designated A from the Bistable Element 72 in the Phase Generator 20 is transmitted to input of Amplifiers 101, 104 and 107 in the set of amplifiers generating a counter clockwise sequential set of signals and the inputs of Elements 111, 114 and 117 in the set of amplifiers generating a clockwise sequential set of signals. In a similar manner, the output signals designated as B and C from the Bistable Elements 74 and 76 of the phase generator are transmitted to the remaining amplifiers as shown. The amplifiers also receive a feedback signal from the set output of their associated bistable element. Bistable Element 121 feeds back a set signal to the alternate inputs of Amplifiers 101 and 111, Bistable Element 122 feeds back a set signal to Amplifiers 102 and 112 respectively, and so forth. In the reset state or Position 1, the clear outputs of Bistable Elements 121 through 124 are ONE and the set outputs are ZERO. As before, a ONE output is indicative of a fluidic signal and a ZERO output is indicative of a lesser amplitude or the absence of a fluidic signal. In the remainder of the bistable elements, the set outputs are ONE and the clear outputs are ZERO. The feedback signals to Amplifiers 101, 111, 102, 112, 103, 113, 104, and 114 are ZERO's and the feedback signals to the remainder amplifiers are ONE's. In the following discussion, it is assumed that the Direction Selector 17 is in the counter clockwise (CCW) position and the fluidic power is applied only to the Amplifiers 101 through 109, therefore, Amplifiers 111 through 119 are inoperative and have no effect on the state of the bistable elements.

Consider the generation of a coded signal by the Phase Generator 20, transmitting ZERO signals to Amplifiers 101, 104 and 109 and ONE signals to the remainder of the amplifiers. The ONE signals make the remainder of the amplifiers nonresponsive to the signals at the alternate input gate. Of these three amplifiers receiving ZERO signals from the code generator, only Amplifiers 101 and 104 have ZERO feedback signals from their associated bistable elements and are the only amplifiers which generate output signals. The output signal from Amplifier 101 is transmitted to the clear gate of Bistable Element 122, generating a ONE signal at V.sub.2. The output signal is also transmitted to the set gate of Bistable Element 127 generating a ZERO signal at V.sub.7. The output of Amplifier 101 therefore does not change the state of the output signals of the Bistable Elements 122 or 127. The output signal from Amplifier 104 is transmitted to the clear gate of Bistable Amplifier 125 producing a ONE signal at V.sub.5 and is also transmitted to the set gate of Amplifier 121 causing it to generate a ZERO signal at V.sub.1. The remaining bistable elements receive ZERO signals at both the set and clear gates, so they do not change state. The ZERO A signal from the phase generator has therefore caused the ONE signal at V.sub.1 to be terminated and caused a ONE signal to be generated at V.sub.5 shifting the ONE signals of the code, one step to the right shown as Position 2 in the Code Table, FIG. 10. The next signal generated by the Phase Generator 20 is one which transmits a ZERO B signal to Amplifiers 102, 105 and 108. Of these amplifiers, Amplifiers 102 and 105 have ZERO feedback signals and will generate output signals. These output signals are transmitted to the clear gates of the Bistable Elements 123 and 126 and to the set gate of Elements 128 and 122 generating ZERO signals at V.sub.2 and V.sub.8 and a ONE signal at V.sub.3 and V.sub.6. In like manner, the C signal produces ONE signals at output of Amplifiers 103 and 106 which clears Bistable Elements 124 and 127 and sets Bistable Elements 129 and 123 generating a ZERO signal at V.sub.9 and V.sub.3 and a ONE signal at V.sub.4 and V.sub.7. The coded signals from the phase generator repeat starting with a ZERO A again causing the ONE output signals to step progressively to the right as shown on the Code Table illustrated in FIG. 10. The fluidic circuits of the code generator are cyclic, therefore, the 9 sequential sets of coded signals are repetitive starting over with the first set after the generation of the 9th or last set. One skilled in the art will quickly recognize that if the counter clockwise set of Amplifiers 101 through 109 are de-energized and fluid power is applied to the clockwise Amplifiers 111 through 119, the sequence of the coded signals generated by the Code Generator 21 will be reversed, and the set of ONE's shown on the table of FIG. 5 will step to the left with each successive input signal from the phase generator.

Referring to FIG. 9, the coded signals from the respective set outputs of the bistable elements in the Code Generator 21 are designated as D1 through D9. The coded output signals D1 through D9 are transmitted to the Interface 22 which comprises nine (9) fluid actuated relay valves 131 through 139 as illustrated in FIG. 11. The relay valves are two position, three way valves controlling the power input to the Fluid Actuator 12 from a Fluid Power Source 140. The valves are normally open communicating fluid power from the Source 140 to the Input Ports 40 of the Fluid Actuator 12. A fluidic signal from the Code Generator 21 closes the valve and vents the output side of the valve to air. The use of fluid actuated valves in the interface buffers the code generator from extraneous signals generated in the fluid actuator, so that these extraneous signals cannot affect the signals generated in the code generator. The illustrated embodiment shows four (4) valves, 131, 132, 133 and 134 in the unactuated state conducting fluid power to the four adjacent chambers of the fluid actuator indicative of Position 1 on the Code Table of FIG. 10. The activated Valves 135 through 139 are venting the five remaining chambers of the actuator to air. One versed in the art will recognize that the illustrated embodiment represents one way to amplify the coded output signal from the code generator, and that other fluidic elements such as fluidic amplifiers or other types of relay valves will function equally well as an interface between the Code Generator 21 and the Fluid Actuator 12.

The signals from the Code Generator 21 are also communicated to the Decoder 23 as shown in FIG. 9. The Decoder 23 is illustrated as a series of Fluidic Amplifiers 151 through 159 which function as OR gates receiving signals from the set outputs of the associated bistable element and the clear output of the preceding bistable element. The amplifiers generate a ZERO output signal only when it receives a ZERO or no signal from both the associated and preceding bistable elements. This condition exists when the set output of the preceding bistable element is a ZERO and the set output of the associated bistable element is ONE and corresponds to the beginning of each series of ONE's in the code illustrated in FIG. 10. The singular ZERO outut signal from the OR amplifiers steps in the same sequential pattern as the coded signals. Therefore, the OR amplifier generating a ZERO signal in response to the signals received from the bistable elements of the code generator corresponds to the coded signal being generated by the code generator.

The signals from the Decoder 23 are transmitted to the Step Selector 14, illustrated in FIG. 9 as a 9 position fluid switch. The function of the switch is to transmit the signal being transmitted to the selected position of the switch to the Inverter Amplifier 161 of FIG. 12 which inverts the signal and transmits the inverted signal to the Clock 19. When the signal generated by the Code Generator 21 does not correspond to the position selected on the switch, the signal transmitted to the selected position from the Decoder 23 is a ONE which is inverted by Amplifier 161 to a ZERO signal. The ZERO signal communicated to the Clock 19 has no effect on the operation of the clock and the clock runs. A ZERO signal, generated by the decoder and transmitted to the selected position of the Step Selector 14, is inverted by the inverter amplifier and becomes a ONE signal. The ONE signal communicated to the Clock 19 stops the clock.

The inverter amplifier illustrated in FIG. 12 as a Fluidic Amplifier 161 functions as follows. Fluid power is supplied to Amplifier 161 from a Fluid Power Source 162 through a two way Switch 163 and a normally closed Momentary Switch 164. The control signal from the Step Selector Switch 14 is communicated to the control gate of the amplifier. The output from the Amplifier 161 is a ZERO when the amplifier receives a ONE signal from the Position Selector 14 switching the signal to the OR output, or when either the Momentary Switch 164 or the Two Position Switch 163 are opened terminating fluid power to the amplifier. The output signal of the Amplifier 161 is ONE when the Momentary Switch 164 and Two Way Switch 163 are closed and the signal from the Step Selector 14 is a ZERO. The ONE output signal generated by the inverter amplifier is the inhibit signal which stops the clock.

The normally closed Momentary Switch 164 and the Two-Position Switch 163 are respectively the Cycle Selector 15 and the Mode Selector 16 illustrated in the block diagram FIG. 1. In normal operation, Switches 163 and 164 are closed applying power to the Amplifier 161. When the signal from the Step Selector 14 is a ZERO indicating the coded signal generated by the code generator corresponds to the selected position of the Step Selector 14 the output signal from the Amplifier 161 is a ONE. Movement of the step selector to an alternate position causes the signal transmitted by the step selector to change from a ZERO to a ONE. This terminates the ONE output from the amplifier and terminates the inhibit signal to the Clock 19 and the clock starts. The clock signals activate the fluidic logic which generates sequential sets of coded signals until the coded signal generated by the Code Generator 21 again corresponds to the new position of the Step Selector 14.

Depressing the Momentary Switch 164 terminates the power to Amplifier 161 causing it to generate a ZERO signal which starts the Clock 19. The duration of the ZERO signal is sufficient to cause the clock to oscillate at least one complete cycle which is sufficient to permit the Code Generator 21 to generate the next sequential coded signal. This removes the ZERO signal from the Step Selector 14 and causes the output of the inverter amplifier to be a ZERO until a complete set of coded signals has been generated by the code generator, and the code generator again generates a signal indicative of the selected position on the step selector. Before the code generator generates a complete set of signals, the momentary switch recloses applying power to the amplifier, so that when the signal transmitted by the Step Selector 14 becomes ZERO again, the amplifier will generate an inhibit signal. Activating the Momentary Switch 164 causes the code generator to generate a set of coded signals equivalent to one revolution of the ring gear in the Fluid Actuator 12.

Activating the two-position Switch 163 to the open position removes the fluid power from the Amplifier 161, causing the amplifier to generate a continuous ZERO signal. The Clock 19 runs free in the absence of an inhibit signal and the fluid logic continues to generate repetitive sequential sets of coded signals as long as the Switch 163 is in the open position. Closing Switch 163 reapplies the fluid power to Amplifier 161 which will generate an inhibit signal when the coded signal generated by the code generator corresponds to the position selected on the Step Selector 14. The ZERO signal transmitted by the step selector will again cause the amplifier to generate an inhibit signal and stop the Clock 19.

The output signals from the code generator are also communicated to the Position Indicator 24. The position indicator may be any type of fluidic device giving a visual indication in response to an input fluidic signal, such as the Bendix Piston Circuit Monitor described in Brochure SL-247 or the Numerical Communicator described in U.S. Pat. No. 3,561,676.

The Direction Selector 17 is illustrated as a three-position Switch 165 in FIG. 13. Power is transmitted to the Switch 165 from a Fluid Power Source 166. The switch in the "CW" (clockwise) position directs this power to Amplifiers 111 through 119 in the Code Generator 21. Likewise, it directs the power to Amplifiers 101 through 109 in the code generator when the switch is in the "CCW" (counter clockwise) position. In the central or "Hold" position, as illustrated in FIG. 13, the power is terminated to both sets of amplifiers and disables the Code Generator 21.

The Reset 25 is illustrated in FIG. 14 as a normally open Momentary Switch 167 which when activated transmits a fluidic signal from a Fluid Power Source 168 to the reset gates of Bistable Elements 71 through 76 in the Phase Generator 20 and the Bistable Elements 121 through 129 in the Code Generator 21. The reset signals are applied to the terminals designated R on the respective bistable elements.

While a specific embodiment has been described, the invention is not to be so limited and many variations are, of course, possible within the scope of the present invention.

Claims

I claim:

1. A fluid stepper motor comprising:

fluid logic means including a control means for providing a selected position input command, said fluid logic means further including means to sequentially generate a series of position coded signals and means responsive to said coded signals for generating a decoded position signal, wherein said position coded signals are sequentially generated until said means for decoding generates a particular decoded signal predetermined by selected input command; and

fluid actuator means including an output member, said output member operative to assume each of a series of corresponding predeterminable positions in response to generation of said series of position coded signals by said fluid logic means, whereby said output member moves sequentially through said series of corresponding predeterminable positions to a position corresponding to said position input command.

2. The stepper motor as claimed in claim 1 wherein said fluid actuator means comprises:

a housing defining a fluid chamber therein;

a rotatably mounted output member;

a ring member eccentrically disposed in said fluid chamber, drivingly engaged with said housing at one point and with the output member at another point; and

means for orbiting said ring member in said fluid chamber, about the axis of said output member, said means including means for applying fluid pressure in defined regions between said ring member and housing members, to generate fluid forces acting thereon, whereby said orbiting of said ring member rotatably drives said output member with relation to said housing.

3. The stepper motor as claimed in claim 2 wherein said means for orbiting said ring member in said fluid chamber comprises:

a plurality of vanes flexibly connecting said ring member with said housing, dividing the space between said ring member and said housing into a plurality of isolated regions of equal angular size; and

a plurality of apertures in said housing for conducting said fluid signals generated by said fluidic logic to said isolated regions, generating a fluid force on the circumference of said ring member.

4. The stepper motor as claimed in claim 1 wherein said fluidic logic means comprises:

clock means, operative to generate oscillating fluid signals of a predeterminable magnitude at a predeterminable frequency and said clock means further including means responsive to an inhibit signal to stop generating said oscillating fluidic signals.

phase generator means responsive to the oscillating signals from said clock means for generating a repetitious set of sequentially phase coded signals.

code generator means responsive to the phase coded signals generated by said phase generator means for generating a repetitive set of sequentially position coded signals, each position coded signal is indicative of a corresponding predeterminable position of said output member and each sequential position coded signal is indicative of a corresponding sequentially adjacent position of said output member in a predeterminable direction;

decoder means responsive to said position coded signals generated by said code generator means for generating decoded signals, wherein each said decoded signal corresponds to an associated position coded signal.

a step selector, responsive to said input command for said output member to move from one position to a second position and to the decoded signals generated by said decoder means, for generating an inhibit signal when said decoded signal to said input command said inhibit signal communicated to said clock means causes said clock to stop.

5. The stepper motor as claimed in claim 4 wherein the fluidic logic further comprises a cycle selector means operative to cause the fluid logic to generate a complete set of coded signals in response to an input command, said cycle selector means is a momentary fluidic switch operative to terminate the inhibit signal generated by the step selector for a period of time sufficient for the code generator means to generate at least one sequential position coded signal.

6. The stepper motor as claimed in claim 4 wherein said fluidic logic further comprises a mode selector responsive to an input command operative to terminate the inhibit signals generated by the step selector causing said fluid logic to generate repetitive sets of sequentially coded signals, said mode selector comprises a two-position fluidic switch, responsive to an input command operative to terminate the inhibit signal generated by the step selector.

7. The stepper motor as claimed in claim 4 wherein said fluidic logic further comprises a reset switch, responsive to an input command, operative to reset said phase generator means to generate a predeterminable phase coded signal and to reset said code generator means to generate a predeterminable position coded signal.

8. The stepper motor as claimed in Claim 4 wherein said clock means comprises:

a variable frequency fluidic oscillator; and

a gateable fluidic amplifier.

9. The stepper motor as claimed in claim 8 wherein said gateable amplifier comprises a means responsive to the oscillating fluidic signals generated by said variable frequency oscillator for generating a first and a second output signal, and said means includes a second input responsive to said inhibit signal generated by said step selector, operative to terminate the response of said gateable amplifier to the signals generated by said variable frequency oscillator.

10. The stepper motor as claimed in claim 8 wherein said variable frequency fluidic oscillator comprises:

fluidic means responsive to input signals operative to generate an output signal; and

feedback means, responsive to said output signal, operative to communicate said output signal to the input of said fluidic means responsive to an input signal, said feedback means delaying said output signal communicated to said input a predeterminable period of time.

11. The stepper motor as claimed in claim 10 wherein said feedback means comprises:

constriction means operative to impede the output signal generated by said fluidic means responsive to input signals;

capacitor means, for accumulating said impeded output signal, whereby the output signal impeded by said constriction means and accumulated by said capacitor means is delayed prior to being communicated to the input of said means responsive to an input, causing the output of said means to oscillate and generate said oscillating fluidic signals.

12. The stepper motor as claimed in claim 4 wherein said phase generator means comprises:

bistable means having a pair of stable states responsive to input signals operative to switch from one stable state to the other and generate output signals; and

input means, responsive to oscillating signals generated by said clock means and the output signals generated by said bistable means operative to generate signals, said signals communicated to said bistable means are operative to cause said bistable means to generate a repetitive set of sequentially phase coded signals.

13. The stepper motor as claimed in claim 12 wherein said means responsive to the oscillating signal generated by said clock comprises:

first means having a plurality of first means elements responsive to said first output signal generated by said clock means, operative to generate an output signal; and

second means having a plurality of second means elements responsive to said second output signal generated by said clock means operative to generate an output signal, said plurality of second means elements is equal in number to said first means elements.

14. The stepper motor as claimed in claim 13 wherein said bistable means comprises a plurality sequentially responsive bistable elements equal in number to the sum of said first means elements and said second means elements, the sequentially responsive bistable elements are alternately associated with said first means elements and said second means elements, and each bistable element has at least one input for each of said bistable elements' stable states, the output signal generated by the first bistable element of said plurality of bistable elements is communicated to the input of the associated first means element, the output signal generated by the sequentially responsive bistable element is communicated to the input of the associated said second means element and the output signals generated by the successive sequentially responsive bistable elements are connected alternately to the inputs of successive alternating first means elements and second means elements, the signal generated by said first means element associated with the first sequentially responsive bistable element is communicated to an input of said associated bistable element and is further communicated to an input of the next sequentially responsive bistable element, the output from the second means element associated with the sequentially responsive bistable element is communicated to the alternate input of said second associated bistable element and one of the inputs of the next sequentially responsive bistable element, the outputs of the successive alternating first means elements and second means elements are alternatively communicated in like manner to the successively responsive bistable elements, with the output of the last second means element communicated to the input of the last sequentially responsive bistable element and further communicated to the alternate input of the first sequentially responsive bistable element forming a cyclic code generator operative to cause the bistable elements to generate a repetitive set of sequentially phase coded signals in response to the signals generated by said clock means.

15. The stepper motor as claimed in claim 4 wherein said code generator means comprises:

bistable means, responsive to input signals operative to generate an output signal; and

input means responsive to said phase coded signals and the signals generated by said bistable means operative to generate an output signal, said output signal is operative to activate said bistable means to generate said repetitive set of sequentially position coded signals.

16. The stepper motor as claimed in claim 15 wherein said input means further comprises:

a second input means, responsive to the phase coded signals generated by the phase generator means and signals generated by said bistable means, operative to generate output signals, said signals operative to cause said code generator means to generate sequential sets of coded signals, the sequence of said coded signals being opposite to the sequence of coded signals generated by said bistable means in response to the signals generated by said first input means; and

a direction selector, having two positions, switchable from one position to the other in response to an input command, said first position operable to apply fluid power to said first input means causing said code generator to generate a repetitive set of sequentially coded signals which sequentially step in a predeterminable direction, and said second position operable to apply fluid power to said second input means, causing said code generator to generate a repetitive set of coded signals which sequentially step in the opposite direction.

17. The stepper motor as claimed in claim 16 wherein said direction selector further comprises a third position, said third position operative to remove fluid power from said first input means and said second input means disabling said code generating means.

18. The stepper motor as claimed in Claim 15 wherein said bistable means comprises a plurality of sequentially responsive bistable elements, each of said bistable elements has a pair of mutually exclusive stable states, switchable from one state to the other in response to input signals, and is operative to generate a first output signal indicative that said bistable element is in its first stable state and a second output signal indicative that said bistable element is in its second state and said coded signal generated by said bistable means is a predeterminable number of sequentially responsive bistable elements generating an output signal indicative of the second bistable state, and the remaining bistable elements generating an output signal indicative of the first bistable state.

19. fluidic element operative to switch said sequentially responsive bistable element to its second state, said signal is also communicated to the input of a second bistable element, which responsively precedes said associated bistable element by a number of bistable elements equal to the number of elements in said predeterminable number of bistable elements generating output signals indicative of the second bistable state, said output signal generated by said fluidic element is operative to switch said responsively preceding bistable element to its first state, whereby the plurality of active elements, in response to a coded signal generated by the phase generator means and signals generated by the associated bistable elements is operative to sequentially step the coded signal generated by said code generator one bistable element in the sequentially responsive direction.

20. The stepper motor as claimed in claim 19 wherein said bistable elements are bistable fluidic flip-flops and said active fluidic elements are fluidic NOR amplifiers.

21. The stepper motor as claimed in claim 19 wherein said fluidic logic further comprises an interface means responsive to the position coded signals generated by said code generator means operative to amplify said position coded signals and communicate said amplified position coded signals to said fluid actuator, said interface includes means operative to buffer said code generator from signals generated in said fluid actuator.

22. The stepper motor as claimed in claim 21 wherein said interface comprises a plurality of fluid actuated two position three-way valves, equal in number to said plurality of bistable elements in said code generator, each valve in said plurality of valves is associated with an associated bistable element in said code generator means, said valves operative to transmit fluid power to said fluid actuator in response to the position coded signals generated by said code generator means.

23. The stepper motor as claimed in claim 19 wherein said decoder comprises a plurality of decoder elements, equal in number to said plurality of bistable elements in said code generator means, each decoder element responsive to an output signal generated by an associated bistable element in said code generator, and further responsive to an output signal of a sequentially responsive bistable element in said code generator means, operative to generate a decoded signal indicative of the existing states of said associated bistable element and said sequentially responsive bistable element.

24. The stepper motor as claimed in claim 23 wherein said bistable elements in said code generator means generate a first output signal having a logic ONE signal indicative that said bistable element is in said first stable state and a logic ZERO signal indicative that said bistable element is in said second bistable state and a second output signal having a logic ONE signal indicative that said bistable element is in said second stable state and a logic ZERO signal indicative that said bistable element is in said first bistable state, and wherein said decoder elements are fluidic OR logic amplifiers responsive to said first output signals generated by said associated bistable elements and said second output signals generated by said sequentially responsive bistable elements, operative to generate a signal in response to a logic ONE signal and terminate said signal in response to simultaneous logic ZERO signals whereby said OR amplifiers generate a signal when the associated bistable element and said sequentially responsive bistable element are in the same bistable state and when said associated bistable element is in the second bistable state and the sequentially responsive bistable element is in the first bistable state, and said OR amplifier is operative to terminate said signal when the associated bistable element is in the first bistable state and the sequentially responsive bistable element is in the second bistable state.

25. The stepper motor as claimed in claim 23, wherein said step selector comprises:

a selector means, having a plurality of positions, each position communicating with an associated decoder element, said selector means switchable from one position to another, in response to an input command, for the actuator output member to move from a first position to a second position, operative to transmit the decoded signal generated by the decoder element; and

an inhibit signal generator, responsive to the signal transmitted by said selector means, operative to generate an inhibit signal when the signal transmitted by the selector means is terminated indicating the code generator means has generated a coded signal corresponding to the particular coded signal predetermined by the selected input command.

26. The stepper motor as claimed in claim 25 wherein said selector means is a multiposition fluidic switch including a single output port and a plurality of input ports equal in number to the plurality of said decoder elements in the decoder wherein each input port is associated with an associated decoder element, said fluidic switch operative to selectively connect said output port with a predeterminable input port of said plurality of input ports in response to said selected input command whereby the signal generated by the associated decoder element of said predeterminable input port is conducted to said output port.

27. The stepper motor as claimed in claim 25 wherein said inhibit signal generator is a monostable fluidic amplifier responsive to the signal generated by the decoder element associated with the predetermined input port of said selector means operative to generate a signal which is the inverse of the signal generated by said decoder element, whereby the monostable amplifier responding to the signal generated by the decoder element transmitted by the selector means generates an inhibit signal when the code generator generates a coded signal corresponding to the selected input command.

28. In combination with a fluid actuator having an output member and means operative to displace said output member to a plurality of positions in response to a set of coded input signals wherein each coded signal of said set of input signals is operative to displace the output member to a predeterminable position the improvement comprising:

clock means operative to generate alternating fluidic signals of a predeterminable magnitude and frequency, said clock means includes means responsive to an input signal operative to stop said clock means from generating said alternating signals;

a phase code generator means generating a repetitious set of sequentially phase coded signals in response to the signals generated by said clock means;

a position code generator means generating a repetitive set of sequentially position coded signals in response to the phase coded signals generated by said phase generator means, each position coded signal corresponds to a predeterminable portion of said output member and each sequential position coded signal of said set of sequentially position coded signals generated by said position code generator means corresponds to a sequentially adjacent position of the output member in a predeterminable direction;

a decoder means generating a sequential set of decoded signals in response to the signals generated by said position code generator means, each decoded signal of said sequential set of decoded signals corresponds to an associated position coded signal; and

a step selector responsive to an input command to displace the output member of the fluid actuator from a first predeterminable position to second predeterminable position including means responsive to the decoded signals generated by said decoder means operative to generate a signal when the decoded signal corresponds to the input command, said signal generated by said step selector communicated to said clock is operative to cause said clock to stop.

29. The combination as claimed in claim 28 wherein aid clock means comprises:

a fluidic oscillator generating oscillating fluidic signals; and

a monostable fluidic amplifier responsive to the oscillating signals generated by said fluidic oscillator, operative to generate a pair of mutually exclusive output signals, said monostable fluidic amplifier includes input means operative to terminate response of said monostable fluidic amplifier to the signals generated by said fluidic oscillator.

30. The combination as claimed in Claim 28 wherein said phase generator means comprises:

bistable amplifier means having a pair of stable states responsive to input signal operative to switch from one stable state to the other and generate output signals; and

phase amplifier means responsive to the signals generated by said clock means and the signals generated by said bistable amplifier means operative to activate said bistable amplifier means generating a repetitive set of sequentially phase coded signals.

31. The combination as claimed in claim 28 wherein said code generator means comprises:

bistable means responsive to input signals operative to generate output signals;

code amplifier means responsive to said phase coded signals and the signals generated by said bistable means operative to activate said code bistable means generating a repetitive set of sequentially positioned coded signals.

32. The combination as claimed in claim 31 wherein said position code generator means further comprises:

second code amplifier means responsive to said phase coded signals and the signals generated by said code bistable means operative to activate said code bistable generating a second sequential set of position coded signals, the directional sequence of said second set of coded signals being opposite to the sequence of the coded signal generated by the code bistable means in response to the signals generated by said first code amplifier means; and

a direction selector having two mutually exclusive positions, switchable from one position to the other in response to an input command, said first position operative to apply fluid power to said first code amplifier means operative to cause said code generator to generate a repetitive set of sequentially position coded signals which sequentially step in a predtermined direction and said second position operative to apply fluid power to said second code amplifier means operative to cause said code generator to generate a repetitive set of sequentially position coded signals which sequentially step in the opposite direction.

33. The combination as claimed in claim 32 wherein the improvement further comprises an interface means, responsive to the position coded signals generated by said code generator means operative to amplify said position coded signals and communicate said amplified position coded signals to said fluid actuator said interface further includes means to buffer said code generator means from said fluid actuator.

34. The combination as claimed in claim 28 wherein said decoder comprises a plurality of decoder amplifiers responsive to the order of the position coded signals generated by said position code generator means operative to operate a set of sequentially decoded signals corresponding to the position coded signal generated by said position code generator means.

35. The combination as claimed in claim 28 wherein said step selector means comprises:

a selector means having a plurality of positions, each position corresponding to a predeterminable position of said output member, said selector means switchable from a first position to a second position by an input command for said output member of the fluid actuator to be displaced from a first predeterminable position to a second predeterminable position, said selector means transmitting said decoded signal corresponding to a predeterminable position coded signal generated by the said decoder; and

an inhibit signal generating means responsive to the signal transmitted by said selector means generating a signal when said predeterminable decoded signal transmitted by the said selector means indicates the code generator means has generated a coded signal corresponding to said second predetermined position, said signal generated by said inhibit signal generating means operative to stop said clock means.

36. The combination according to claim 28 wherein the fluid logic further comprises:

a cycle selector means operative to cause the fluid logic to generate one complete set of position coded signals in response to an input command;

a mode selector means responsive to an input command operative to termiante said inhibit signals generated by said step selector causing said fluid logic to generate repetitive sets of sequentially position coded signals; and

a reset means operative to cause said fluidic logic to generate a position coded signal corresponding to a predeterminable position of said output member.