Rotary drive device and control method thereof

Abstract

Provided is a rotation drive device that has a wide rotary driving range, e.g. a rotary driving range of 0°-180°. Disclosed is a rotation drive device comprising a crank member rotatable about a crank axis, a first cylinder having a first piston and rotatable about a first cylinder rotation axis, and a second cylinder having a second piston and rotatable about a second cylinder rotation axis. The crank member and the first piston are coupled for rotation about a first piston rotation axis spaced from the crank axis. The crank member and the first piston are coupled for rotation about a second piston rotation axis spaced from the crank axis.

Claims

1. A rotation drive device comprising: a crank member rotatable about a crank axis, a first cylinder having a first piston and rotatable about a first cylinder rotation axis, and a second cylinder having a second piston and rotatable about a second cylinder rotation axis, wherein; the crank member and the first piston are coupled for rotation about a first piston rotation axis spaced from the crank axis, the crank member and the second piston are coupled for rotation about a second piston rotation axis spaced from the crank axis, and the first piston comprises a curved portion complementary to the crank axis.

2. A rotation drive device according to claim 1, wherein an angle formed by a straight line connecting the crank axis and the first piston rotation axis and a straight line connecting the crank axis and the second piston rotation shaft is 30 to 60′.

3. A rotation drive device according to claim 2, wherein the angle formed by the straight line connecting the crank axis and the first cylinder rotation axis and the straight line connecting the crank axis and the second cylinder rotation axis is 30 to 60°.

4. A rotation drive device according to claim 1, wherein the angle formed by a straight line connecting the crank axis and the first cylinder rotation axis and a straight line connecting the crank axis and the second cylinder rotation axis is 30 to 60°.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a rotation drive device 100 according to an embodiment of the present invention. The main cylinder 6a is at the bottom dead center. (a) is a front view and (b) is a side view.

(2) FIG. 2 shows a rotation drive device 100. The main cylinder 6a is located between the bottom dead center and the top dead center.

(3) FIG. 3 shows a rotation drive device 100. The main cylinder 6a is at top dead center.

(4) FIG. 4 shows the relationship between angles θ and β and torques T1 and T2 in the rotation drive device 100.

(5) FIG. 5 shows a preferred embodiment of a servo valve unit 60 capable of driving cylinders 6a and 6b and a control system 200 thereof.

(6) FIG. 6 shows another embodiment of servo valve unit 60A and its control system 200A.

(7) FIG. 7 shows a block diagram of a conventional pneumatic servo control.

(8) FIG. 8 shows a conventional spool type servo valve.

(9) FIG. 9 shows a conventional flapper type servo valve.

(10) FIG. 10 shows a conventional rotation drive device 100P for rotating an arm 2 with one cylinder 6.

MODE FOR CARRYING OUT THE INVENTION

(11) FIGS. 1 to 3 show a rotation drive device 100 according to an embodiment of the invention. In FIGS. 1 and 3, the main cylinder 6a is at bottom dead center and the top dead center, respectively, and in FIG. 2, the main cylinder 6a is in an intermediate position.

(12) The rotation drive device 100 includes a crank member 2, a main cylinder (first cylinder) 6a, and a sub-cylinder (second cylinder) 6b. The main cylinder 6a has a main piston (first piston) 7a that moves forward and backward in a linear direction, and the sub-cylinder 6b has a sub-piston (second piston) 7b that moves forward and backward in a linear direction. The cylinders 6a and 6b of the present embodiment are pneumatic type, but may be hydraulic type. It is also possible to use an actuator of other types (or any other type of drive member) which is capable of moving the pistons 7a and 7b linearly forward and backward. In a typical cylinder, the piston and the piston rod move together. “Piston” in the present application may mean a piston rod or a piston and a piston rod.

(13) The crank member 2 is rotatable about a crank rotation axis (crank axis) 3. The main cylinder 6a is rotatable about a main cylinder rotation axis (first cylinder rotation axis) 5a, and the sub-cylinder 6b is rotatable about a sub-cylinder rotation axis (second cylinder rotation axis) 5b.

(14) The main piston 7a and the crank member 2 are rotatably connected to each other by a main piston rotation axis (first piston rotation axes) 4a separated from the crank rotation axis 3, and the sub-piston 7b and the crank member 2 are rotatably connected to each other by a sub-piston rotation axis (second piston rotation axis) 4b separated from the crank rotation axis 3. Therefore, the main cylinder 6a, the sub-cylinder 6b, and the crank member 2 form a link structure (four-section link structure) in which the rotation axes 5a and 5b are fixed ends and the rotation axes 4a and 4b are free ends. Although a disk-shaped crank member 2 is shown in the drawing, the shape, structure, and the like of the crank member 2 are arbitrary as long as the link structure can be configured. The rotation axes 3, 5a and 5b can be fixed to a common base 1, and the rotation axes 4a and 4b can be fixed to the crank member 2.

(15) The crank member 2 may have an arm 2a that rotates integrally with the crank member 2. The arm 2a can be used, for example, as a limb of a robot or the like. The mounting angle of the arm 2a is arbitral. In the examples of FIGS. 1 to 3, the arm 2a and the crank member 2 are fixed so that the crank rotational angle (the angle formed between the arm 2a and vertical direction) θ is 0° and 180° when the main piston 7a is at the bottom dead center (see FIG. 1) and the top dead center (see FIG. 3), respectively. In the drawings, a boss 2b is disposed between the crank member 2 and the arm 2a, and the crank rotation axis 3 is supported in the opening of the boss 2b, but the crank rotation axis 3 may be supported on the outer side of the boss 2b via bearings.

(16) The piston 7a may have a curved portion (bend) 8 so that the main piston 7a does not interfere with the crank rotation axis 3 when the arm 2a (or the crank member 2) is rotated to an angle of 180° or more. The curved portion 8 may have a shape complementary to the crank rotation axis 3, for example, an annular or ring or arc shape of about 180°. The annular shape, etc., may have an inner diameter that is larger than the outer diameter of the crank rotation axis 3 or the boss 2b.

(17) It is desirable that the respective rotation axes 3, 4a, 4b, 5a and 5b are arranged so that the torque T2 generated by the sub-piston 7b in the crank member 2 becomes large in the vicinity of the top dead center or the bottom dead center where the rotational torque T1 generated by the main piston 7a in the crank member 2 becomes small. Furthermore, it is also desirable that the cylinders 6a and 6b do not interfere with each other, and that the components are arranged in a compact manner (the volume occupied by the device 100 is small). In view of these, the angle A formed by 5a-3-5b and/or the angle B formed by 4a-3-4b is preferably 30 to 60°, more preferably 40 to 50°. FIGS. 1 to 3 are the optimal case, in which the sub-piston rotation axis 4b rotates in the range of 0=−90 to +90° when the angles A and B are 45° and the main-piston rotation axis 4a rotates in the range of 0=0 to 180°. Of course, other arrangements are possible depending on the volume, shape, etc. of the installation space of the rotation drive device 100. For example, the angle A may be around 90° and the angle B may be around 0°. The piston rotation axes 4a and 4b may be a common axis.

(18) In the rotation drive device 100, the relationship between the angles θ and β and the torques T1 and T2 is as shown in FIG. 4. Since the torques T1 and T2 become maximum when the pistons 7a and 7b is at a tangential line of the circle which is the trajectory of the rotation axes 4a and 4b, respectively, the torque T1 becomes maximum in the vicinity of 90° (θ<90°), and the torque T2 becomes maximum in the vicinity of ±90° (−90°<β<90°), as shown in the drawing.

(19) In this embodiment, the phase differences between the angles θ and β are about 90°, and the regions Sa and Sb in the vicinity of β=±90° where the torque T2 of the sub-cylinder 6b increases correspond to the regions Mb and Mc in the vicinity of θ=0° or 180° where the torque T1 of the main cylinder 6a decreases. For this reason, a sufficiently large torque T2 can be obtained even in the vicinity of θ=0° or 180°, where a sufficient torque T can not be obtained by the conventional rotation drive device 100P. As a result, the crank member 2 (arm 2a) can be driven in rotational angular ranges of θ=0° to 180° or more. Further, since the combined torque T1+T2 can be leveled, the stability and flexibility of rotation driving can be improved. The phase difference between the angles θ and β is preferably 80° to 100°, and particularly preferably 85° to 95°. By optimizing the outputs of the cylinders 6a and 6b, the positional relationships between the rotation axes 3, 4a, 4b, 5a and 5b, and the like, the combined torques T1+T2 can be further leveled.

(20) In the rotation drive device 100, when the arm 2a is rotated in a specific direction, it is desirable to perform a control (control 1) of reversing the drive direction of the sub-cylinder 6b at a boundary in the vicinity of β=0°, and similarly reversing the drive direction of the main cylinder 6a at a boundary in the vicinity of θ=0° or 180°. By this, it is possible to prevent the torques T1 and T2 from acting in the opposite direction.

(21) The main cylinder 6a can be set in an unloaded state (the state where both of the piston chambers are exhausted) in the regions Mb and Mc, and/or the sub-cylinder 6b can be set in an unloaded state (the state where both of the piston chambers are exhausted) in the region Sc. These controls can be referred to as control 2. For example, the cylinders 6a and 6b can be unloaded by opening both of the chambers to atmospheric pressure. As a result, the outputs (resistances) of the cylinders 6a and 6b in the regions Mb, Mc, and Sc become zero or almost zero, so that the problems of the torque T1 and the torque T2 acting in opposite directions can be solved. In addition, since the timing of reversing the driving direction is not strictly required, the control can be made easy.

(22) When the cylinders 6a and 6b are pneumatic cylinders, the air is compressible, and the torque T1 in the regions Mb and Mc and the torque T2 in the region Sc are very small. Therefore, the strict timing of the control 1 is not required, and a great problem does not occur even if the control 2 is not performed. On the other hand, when the cylinders 6a and 6b are hydraulic cylinders or ball screw actuators, or the like, there is a high possibility that power loss, damage due to overload, or the like will occur due to the torques T1 and T2 in opposite directions, so that the control 1 needs to be performed more strictly, and the necessity of the control 2 increases.

(23) FIG. 5 shows a preferred form of a pneumatic servo valve unit 60 and its control systems 200 that can be suitably used to drive the cylinders 6a and 6b of the rotation drive device 100. The control system 200 includes a servo valve unit 60, a pneumatic cylinder 40 corresponding to a main cylinder 6a or a sub-cylinder 6b, and a controller 50. The servo valve unit 60 has a valve body 10 in which a hollow space such as a common flow path 11, a supply port (supply flow path) 12, an exhaust port (exhaust flow path) 13, and a drive air port (drive air flow path) 14 are formed. The valve body 10 may be an assembly of a plurality of parts made of metal, plastic, or the like.

(24) One end of the supply port 12 is connected to the common flow path 11 via a first valve portion 20R capable of a pulsed opening and closing operation in accordance with the first electric pulse S1. The other end may have a connection part 12a for connecting to a source of high pressure air, such as a compressor or cylinder, for supplying high pressure air S. One end of the exhaust port 13 is connected to the common flow path 11 via a second valve portion 20L capable of a pulsed opening and closing operation in accordance with the second electric pulse S2. The other end of the exhaust port 13 is connected to the outside (e.g., atmospheric pressure) through an opening 13a in the outer wall 10a of the valve body 10. One end of the drive air port 14 is constantly connected to the common flow path 11. The other end of the drive air port 14 may have a connection part 14a, such as a joint, for connecting to one of the cylinder chambers 41 of the pneumatic cylinder 40. In the figure, the common flow path 11, the supply port 12 and the exhaust port 13 extend in the axial direction of the valve body 10, and the drive air port 14 is drawn out in the radial direction from a suitable position of the common flow path 11, however, other embodiments are possible.

(25) The first valve portion 20R and the second valve portion 20L of the present embodiment have the same symmetrical structure. In the drawings, for simplicity, reference numerals of some members of the second valve portion 20L are omitted. Hereinafter, when it is not necessary to distinguish the first valve portion 20R and the second valve portion 20L, they are simply referred to as the valve portion 20. The valve portion 20 of the present embodiment includes a nozzle 21 formed at the tip of the supply port 12 and the exhaust port 13, a valve seat 22 which can close the nozzle 21 by abutting against the tip of the nozzle 21, a magnetic member 23 which can move in the axial direction integrally with the valve seat 22, a biasing member 24 such as a spring for biasing the valve seat 22 and the magnetic member 23 in the axial direction, a fixed magnetic core 25 arranged apart from the nozzle 21 in the axial direction, and a solenoid 26 for exciting the fixed magnetic core 25. The magnetic member 23 may have a side wall 23a complementary to the outer shape of the nozzle 21 for guiding the axial movement of the magnetic member 23.

(26) In a state in which the solenoid 26 is not energized, the valve seat 22 is in contact with the nozzle 21 by the force of the biasing member 24, so that the valve portion 20 is OFF (closed state), and when the solenoid 26 is energized, the valve seat 22 is separated from the nozzle 21 by the magnetic force of the fixed magnetic core 25, and the valve portion 20 is turned ON (open state).

(27) The space between the nozzle space 11a around the valve seat 22 of the first valve portion 20R and the nozzle space 11a around the valve seat 22 of the second valve portion 20L is always connected by the common flow path 11. That is, the nozzle space 11a and the outer peripheral space 11b around the fixed magnetic core 25 are connected via an axial through groove 11c formed in the side surface of the nozzle 21, and the outer peripheral space 11b and the spring space 11d accommodating the biasing member 24 are connected by a radial through hole 11e. A plurality of the through grooves 11c and the through holes 11e may be formed at intervals in the circumferential direction of the nozzle 21. The spring spaces 11d of the left and right valve portions 20R and 20L are connected to each other by a communication passage 11f.

(28) Hereinafter, the left half and the right half of the servo valve unit 60 may be referred to as servo valve elements 30A and 30B.

(29) The pneumatic cylinder 40 has cylinder chambers 41 and 42, a piston 43 corresponding to the main piston 7a or the sub-piston 7b, and a biasing means 44 such as a spring for biasing the piston 43, and the axial position of the piston 43 can be detected by a position sensor 45. The shape of the cylinder chambers 41 and 42 is arbitrary, and the cylinder chambers 41 and 42 may have a shape other than a cylindrical shape. The controller 50 generates first and second electric pulses S1 and S2. The first and second electric pulses S1 and S2 may be signals depending on the position of the piston 43, the desired speed, etc. The first and second electric pulses S1 and S2 may have a duty ratio that depends on the position or speed of the piston 43. The controller 50 may be, for example, a computer.

(30) When the electric pulse S1 is turned ON and the electric pulse S2 is turned OFF, the first valve portion 20R is turned ON and the second valve portion 20L is turned OFF, so that the high-pressure air S is supplied from the supply port 12 to the cylinder chamber 41 via the common flow path 11 and the drive air port 14, and the piston 43 can be moved leftward. When the electric pulse S1 is turned OFF and the electric pulse S2 is turned ON, the first valve portion 20R is turned OFF and the second valve portion 20L is turned ON, the air in the cylinder chamber 41 is discharged to the outside from the opening 13a through the drive air port 14, the common flow path 11 and the exhaust port 13, and the piston 43 is moved rightward by the force of the biasing means 44. When both of the electric pulses S1 and S2 are turned OFF, the supply and exhaust to and from the cylinder chamber 41 are stopped.

(31) In this manner, the output air pressure to the cylinder chamber 41 which opens and closes the valve portions 20R and 20L in a pulsed manner can be switched on/off (supply/stop can be switched or exhaust/stop can be switched) in a pulsed manner by the control of the electric pulses S1 and S2. By speeding up the switching, it is possible to precisely and smoothly control the position of the piston 43. Basically, when the duty ratio of the electric pulse S1 or S2 is increased, the driving force of the piston 43 is increased, and when the duty ratio is decreased, the driving force of the piston 43 is decreased. Therefore, when the difference Δd between the current position and the target position of the piston 43 is large, the duty ratio is increased to move the piston 43 at a high speed, and when the difference Δd becomes small, the duty ratio is decreased to decelerate the piston 43, and the duty ratio is set to zero (signal stop) to stop the piston 43. However, in order to perform rapid positioning and follow-up control, it is preferable to perform control such that the movement is started at a slow speed, gradually accelerated, and then decelerated, and stopped. In addition, it is preferable to control to freely change the speed in accordance with the kind of the task of the robot or the like. For these controls, it is preferable to heighten the speed of the supply/exhaust switching, and it is desirable that the maximum frequency of the supply/exhaust switching be 100 Hz or more, preferably 300 Hz or more, more preferably 500 Hz or more, and particularly preferably 1000 Hz or more. In the servo valve unit 60 of the present embodiment, high-speed switching of 300 to 500 Hz is realized in a prototype stage, and it has been confirmed that a motion close to a human can be realized in a prototype of an arm unit of a humanoid robot incorporating a pneumatic cylinder driven by the servo valve unit 60. The inventors of the present application believe that 1000 Hz can be achieved by future improvements.

(32) The servo valve unit 60 may further include a silencer plate 16 for reducing exhaust noise. The silencer plate 16 is attached to the valve body 10 at a position overlapping with the opening 13a, i.e., at a position blocking the opening 13a, with a gap G from the outer wall 10a. The silencer plate 16 preferably has a sufficiently larger area than the opening 13a and is parallel to the outer wall 10a. The exhaust port 13 may have a cavity 13b having a large cross-sectional area on the opening 13a side. Since the exhaustion air gradually expands from the nozzle 21 to the outer periphery of the gap G through the cavity portion 13b, it is possible to effectively alleviate the burst sound at the time of exhaustion to the atmosphere. When the circumferential length of the hollow portion 13b is L, the gap is G, and the opening area of the nozzles 21 is SA1, it is desirable that L×G is approximately equal to SA1. The cross-sectional area of the exhaust port 13 from the nozzle 21 toward the opening 13a may be increased in multiple stages or gradually. If the gap G is increased or decreased in accordance with the exhaust pressure by fixing the silencing plate 16 with a elastic member 16a having a spring property or the like, the exhaust pressure is further leveled to improve the silencing effect. Although the above arrangement is not 100% muffling, a significant muffling effect can be achieved while achieving the space saving which is an important object of the present invention.

(33) FIG. 6 shows another embodiment of a servo valve unit 60A and its control system 200A. The servo valve unit 60A has a structure in which two servo valve units 60R and 60L are housed in a single valve body 10 so that their supply ports 12 face each other. The servo valve unit 60A includes four servo valve elements 30AL, 30AR, 30BL, and 30BR. The servo valve units 60R and 60L have the same configuration as that of the servo valve unit 60, but the two supply ports 12 are connected at the center and drawn out from the side surface of the valve body 10. The drive air ports 14 are drawn out from the side surface of the valve body 10 and connected to the respective cylinder chambers 41 and 42 of the pneumatic cylinder 40. Connection parts 12a and 14a of the supply port 12 and the drive air port 14 are preferably provided on the same side of the valve body 10 and/or adjacent to each other.

(34) The controller 50 applies electric pulses S1 and S2 to the left and right servo valve units 60R and 60L in accordance with the piston position, the desired piston speed, and the like of the pneumatic cylinder 40. In this example, an electric pulse S1 is applied to servo valve elements 30AL and 30BR, and an electric pulse S2 is applied to servo valve elements 30BL and 30AR. As a result, the servo valve units 60R and 60L operate in the same manner as the servo valve unit 60 to drive the piston 43 to the left and right. In the wiring configuration in the figure, the servo valve device 30AL and the servo valve device 30BR are simultaneously excited, and the servo valve device 30BL and the servo valve device 30AR are simultaneously excited. However, it is also possible to independently excite each of the valve devices, and the pulse numbers of the electric pulses to the servo valve devices 30AL, 30AR, 30BL and 30BR may be changed independently.

(35) In the servo valve units 60 and 60A, the pneumatic cylinder 40 (6a,6b) can be controlled with high accuracy without using a servo amplifier, and the manufacturing accuracy or bleeding of air as in the conventional pneumatic servo valve is unnecessary. In particular, by setting the ON/OFF switching speed of the valve portion or the supply/exhaust switching speed of the pneumatic cylinder to 100 Hz or more, smooth control of the moving speed and stopping position of the pistons 43 (7a,7b) can be achieved. By setting the switching speed to 300 Hz or more, more preferably 500 Hz or more, more preferably 1000 Hz or more, the controllability of the moving speed and the stop position of the pistons can further be enhanced. It should be noted that as each of the cylinder chambers and flow paths has a certain volume, and the piston has a moment of inertia and a slight friction, the piston operates smoothly without any trouble even if the supply and exhaustion of air are switched in a pulsed manner.

(36) The inventor of the present application produced a prototype of the rotation drive device 100 using the servo valve unit 60A. The cylinders 6a and 6b of the rotation drive device 100 had an inner diameter of 60 mmϕ, and high-pressure air of 0.4 MPa was used. The size of the servo valve unit 60A is 20×25×70 mm. Using this prototype, it was confirmed that the rotation speed and the stop position can be freely controlled in the range of 0° to 180° with attaching a weight of up to 5.3 Kg to the tip of an iron arm with 63 cm length. Videos showing the movement of the prototype was made, and uploaded as a youtube video (URL: https://youtu.be/mAEVludfmno). In addition, an arm unit of a human-sized humanoid robot incorporating 8 sets of the above prototypes was prepared, and it was confirmed that it was possible to freely raise and lower a weight of 12.5 kg attached to the tip (palm part) of the arm. The state of the movement is shown in the youtube video (URL: https://youtu.be/7cVjNuoC_w8, https://youtu.be/FxbWDolcv_k, https://youtu.be/5XO8cX9oREA, https://youtu.be/0qnxH6PFCwo)). In this arm unit, all eight servo valve units are accommodated in the upper arm portion.

(37) Since the motive for the development of the present invention is to realize a humanoid robot (or humanoid disaster robot), the present invention has been mainly described as being applied to a humanoid robot, but the present invention is also applicable to various robots other than the humanoid robot (for example, a lizard type, a centipede type, a multi-legged robot, a four-legged animal robot, or the like). The present invention can be applied to robots other than disaster robots, such as nursing care robots and work assisting robots. Furthermore, the present invention is applicable to fields other than robots. The present invention is widely applicable to driving of a movable member (arm la) in an industrial machines or household appliances.

(38) The cylinder (first cylinder and second cylinder) of the present application is a linear actuator capable of linearly moving a piston (or a drive rod) forward and backward. The cylinder of the present application includes not only a cylinder type actuator, but also other types of actuators such as a ball screw type actuator and a ball spline type actuator. For use in a humanoid robot, a pneumatic cylinder capable of absorbing a reaction force by compressibility of air is preferred.

(39) The dimensions, shapes, arrangements, numbers, materials, characteristics, and the like of the rotation drive device, the servo valve unit, or the control system described in the above embodiments, or their constituent elements are examples, and these can be appropriately changed within the scope the invention described in the claims.

EXPLANATION OF REFERENCE SYMBOLS

(40) 1 base

(41) 2 crank member

(42) 2a arm

(43) 2b boss

(44) 3 crank rotation axis

(45) 4a, 4b first and second piston rotation axes

(46) 5a, 5b first and second cylinder rotation axes

(47) 6a, 6b first and second cylinders

(48) 7a, 7b first and second pistons

(49) 8 curved part

(50) 10 valve body

(51) 11 common flow path

(52) 12 supply port

(53) 13 exhaust port

(54) 14 drive air port

(55) 16 silencer

(56) 50 controller

(57) 60, 60A Servo valve unit

(58) 100 rotation drive

(59) 200, 200A control system