JP4372816B2 - Leg joint drive device for legged robot and control method thereof - Google Patents

Description

  The present invention relates to a leg joint drive device for a legged robot such as a biped robot and a control method therefor.

Many researches have been conducted on biped robots, quadruped robots, or legged robots with five or more legs. There are two ways to implement legged robot walking. That is, they are passive walking and active walking (for example, refer nonpatent literature 1). Passive walking is a walking form that moves down a gentle downhill without mounting any actuator on the robot or using any mounted actuator. This walking is closest to walking that can be observed in nature, and is a walking form that enables walking with less energy consumption, and the specific mechanical movement cost c _mt obtained by dividing the energy consumption by the product of the weight of the robot and the movement distance. Is 0.1 or less (see Non-Patent Document 2, page 1083). However, since there is no energy supply, continuous walking on flat ground is impossible, and since control is not performed, walking on wasteland is not possible.

  On the other hand, the most commonly performed walking with a walking robot is active walking (see, for example, Patent Document 1 and Patent Document 2). In the robots disclosed in these patent documents, the joint and the drive motor are always coupled, and the joint is always driven and controlled. As a result, energy consumption increases, and the energy cost for movement represented by total energy / (robot weight × movement distance) becomes 3 or more (see Non-Patent Document 2, page 1083).

  On the other hand, in recent studies (Carnegie Mellon University (USA), MIT (USA), Delft University (Netherlands)), a passive walking mechanism that has traditionally been capable of only gentle downhill walking is necessary for walking on flat ground. Experimental results of “passive dynamic walking” that supplies energy and is close to passive walking even on flat ground have been published (see, for example, Non-Patent Document 3 and Non-Patent Document 4).

T. McGeer, `` Passive dynamic walking '' Int. J. Robot. Res., Vol. 9, no. 2, pp. 62-82, Apr. 1990. S. Collins, A. Ruina, R. Tedrake, M. Wisse, `` Efficient Bipedal Robots Based on Passive Dynamic Walkers, '' Science, vol. 307, pp. 1082-1085, Feb. 2005. S. Collins, A. Ruina, M. Wisse, "A Three Dimensional Passive-Dynamic Walking Robot With Two Knee and Legs," Int. J. Robotics Research, Vol. 20, M. Wisse, DGE Hobbelen, AL Schwab, `` Adding an upper body to passive dynamic walking robots by means of a bisecting hip mechanism, '' IEEE Trans.Rob., Vol. 23, no. 1, pp. 112-123, Feb .2007. JP 09-094784 A JP 09-094785 A

  However, in the technologies disclosed in Non-Patent Document 3 and Non-Patent Document 4, a driving technique such as a robot disclosed in Patent Document 1 and Patent Document 2, that is, a combination of a servo motor and a speed reducer, or an artificial muscle (for example, , McKibben muscles, (Non-Patent Document 4, p.118, Fig. 9), a dedicated device is required to separate the motor and joints necessary to realize passive walking. As a result, the joints of the robot become large and complicated, and in the case of artificial muscles (for example, McKibben muscles), the energy source is compressed gas, which makes it difficult to control as well as performance and cost. There is a problem.

  The present invention has a simple structure and a passive walking on a gentle downhill (completely separating the joint and the drive motor as a drive system), and a passive dynamic walking on a flat ground and a gentle uphill (only the necessary energy is consumed). Supply), and active walking (steeply connecting the drive motor and the joint) such as steep slopes and up and down stairs, without using any additional device or switching mechanism. It is an object of the present invention to provide a leg joint drive device for a legged robot that can be realized only by control and a control method thereof.

The invention according to claim 1 for solving the above-mentioned problem is to fix at least one end of at least two wires / strips to the axial center of the rotary motion output shaft end and to rotate the other end of the wires / strip to the rotation of the moving body to perform the movement along the motor output axis, and fixed with a symmetrical about the axis of the rotary motion output shaft from the axis at a site spaced apart a predetermined distance a, also the predetermined distance a, the line- Article of length L, a radius R of the wire-strip, the rotary motion output shaft the rotary movement of the moving body and the torque T of the drive motor with a rotational angle α and the parameters of the motion displacement x of the movement of As a parameter governing the relationship with the tensile force F that is displaced in the direction of the output shaft, the rotation of the rotary motion output shaft causes twisting of the at least two wires / stripes by the rotation of the rotational motion output shaft. Along the motion output axis direction Converting the displacement of the moving body to perform the movement, also the movement body motion converter comprising configured to convert the displacement into rotational motion of the rotary motion output shaft of the legged robot hip joint, knee joint, And a leg joint drive device for a legged robot, which is mounted on at least one of the ankle joints.

According to the second aspect of the present invention, at least one end of at least two wires / strips is fixed to the axial center of the rotary motion output shaft end, and the other end of the wire / strip is moved along the rotational motion output shaft direction. The moving body to be performed is fixed to a portion which is symmetric with respect to the axis of the rotary motion output shaft and is separated from the axis by a predetermined distance A, and the predetermined distance A, the length L of the line / strip, the line / strip And the rotational angle α of the rotary motion output shaft as parameters of the motion displacement amount x of the moving body, and the torque T of the drive motor and the tensile force F that displaces the moving body in the direction of the rotary motion output shaft. As a parameter governing the relationship between the rotational motion output shaft, the rotation of the rotational motion output shaft causes twisting of the at least two lines / strips, and the rotational motion of the rotational motion output shaft moves along the rotational motion output shaft direction. Converted to displacement of the moving body, and A motion conversion device configured to convert the displacement of the moving body into a rotational motion of the rotational motion output shaft is attached to at least one of a hip joint, a knee joint, and an ankle joint of a legged robot, and the motion The conversion device detects at least one of the pulling force F and the rotation angle of the mounted joint, and the pulling force F and / or the rotation angle of the mounted joint is desired based on the detection result. A control method for a leg joint drive device of a legged robot, wherein either one or both of the rotation angle α and the torque T is controlled so as to obtain a control amount of

Invention of claim 3, wherein the drive motor in a state where the legged with leg joint driving apparatus for a robot, not the rotation angle of the rotary motion output shaft not crowded twisting the strip the wire-according to claim 1 the make state the mounted joint was isolated as a drive system, tighten performed passive walking legged robot, the torque to the mating attachment joint applied by the drive motor only in a predetermined range of the walking cycle of the legged robot with , tighten performed passive dynamic walking to the legged robot, further characterized in that the object to be mounted joint and the drive motor which accounts made active walking as coupling state as the driving system via the Article the line-leg It is a control method of the leg joint drive device of a robot.

  According to the present invention, a leg that can realize three types of walking, that is, passive walking, passive dynamic walking, and active walking, by simply controlling the drive motor without requiring a special additional device or switching mechanism, with a simple structure. A leg joint drive device for a robot and a control method therefor can be provided. In addition, walking with low energy consumption is possible. Furthermore, by loosening the line / strip by reverse rotation of the drive motor, the joint of the robot leg and the drive motor can be separated as the drive system to make the joint free, and humans and the robot contacted in unexpected situations Sometimes it is possible to increase the safety against human harm, and it is possible to increase the probability of preventing a robot failure even when the robot falls.

  First, the leg joint drive mechanism of a conventional legged robot will be described. When passive dynamic walking is realized on a flat ground, the hip joint is driven and a lock mechanism is mounted on the knee to fix the ankle and the sole is, for example, As shown in Fig. 5 on page 611 of Non-Patent Document 3, make it circular. In order to continue walking, at the moment when the supporting leg changes to a free leg, the leg is unlocked and a torque is temporarily applied to the hip joint so that the leg that has become a free leg is kicked in the forward direction. However, in a conventional joint drive device comprising a combination of a servo motor and a gear, the free leg cannot be freely swung in the forward direction unless a dedicated clutch mechanism or the like is mounted. It is necessary to follow the movement. This increases energy consumption.

  In the case of pneumatic artificial muscles, the legs can be freely shaken, but accurate and quick control is difficult, so that it is difficult to realize a stable walking and performance is inferior.

In the present invention, a drive mechanism for driving the joint will be described. The basic form of the joint drive mechanism is shown in FIG. One end of at least two wires / stripes 13 is fixed to the shaft center of the rotary motion output shaft 12 of the drive motor 11, and the other end is fixed to the linear motion body 14 from the shaft center of the rotary motion output shaft 12 in the radial direction. Are fixed apart by a predetermined distance A. When the rotary motion output shaft 12 rotates by an angle α, the lines / stripes 13 are twisted together, and the linear motion body 14 is displaced by x along the axial direction of the rotary motion output shaft 12. This displacement is a linear direction or an arcuate displacement, for example, when the joint is rotated.

Here, in order to obtain a sufficient stroke in a minimum space, the radial direction from the axial center of the rotary motion output shaft 12 when the other end of the line / strip 13 which is a design parameter is fixed to the linear motion body 14 is used. It is necessary to appropriately select the predetermined distance A and the length L of the line / strip 13. Further, the relationship between the torque T of the motor (rotary drive source) 11 and the tensile force F that displaces the moving body 14 in the axial direction of the drive motor due to the twisting of the wire / strip 13 is the thickness (diameter) of the wire / strip 13. Therefore, in order to convert the torque T of the motor (rotary drive source) 11 into a large tensile force, it is desirable to use a thin wire / strip 13.

When two lines / stripes 13 are used, the relationship between the rotation angle α (rad) of the rotary motion output shaft 12 and the motion displacement amount x of the linear motion body 14 is

Given in. Here, L is the length of the wire / strip 13 when the wire / strip 13 is completely solved, and A is a radius from the axis of the rotary motion output shaft 12 of the fixed portion of the linear motion body 14 of the wire / strip 13. The distance in the direction, R, is the radius of the line / strip 13. However, R << L and R << A.

The theoretical maximum stroke x _max and the maximum rotation angle α _max (rad) at that time are determined from the length L and radius R of the selected wire / strip 13 and the radial distance A from the axis of the rotary motion output shaft 12. ,

Given in.

  Further, the relationship between the torque T of the motor 11 and the tensile force F is

Indicated by

As the wire / strip 13, a high-strength fiber having flexibility, excellent tensile strength, appropriate rigidity, and sufficient durability against repeated bending, such as carbon fiber, Kevlar, Zylon, nylon, etc. is used. be able to.
In addition, the cross-sectional shape of the wire / strip 13 can be a circle, a polygon, or a rectangle (ribbon). When a rectangular shape (ribbon) is used, a larger cross-sectional area can be obtained with the same torque- to- tensile force conversion ratio, and the force capacity that can be transmitted can be increased.

  Furthermore, in order to increase the durability of the wire / strip 13, the wire / strip 13 is coated with a material having a small friction coefficient such as tetrafluoroethylene resin (registered trademark: Teflon), nylon, etc. It is good to reduce the friction between strands. In addition, for the purpose of improving the durability (life) of the wire / strip 13, an appropriate lubricant (grease, oil, powder material and a combination thereof) is applied to reduce the friction between the wires / strip 13 Can be applied to. For example, organic, inorganic grease, oil, ethylene tetrafluoride resin (registered trademark: Teflon) powder, nylon powder, Molycoat, and combinations thereof can be used.

  In the leg joint drive device and control method thereof for the legged robot of the present invention, the foot structure is the same as the conventional one, and the drive device shown in FIG. In order to drive the leg 6 of the robot, this drive device has one end fixed to the shaft center of the drive motor 1 fixed to the robot body 5 and the rotation output shaft 2 of the drive motor 1 and the other end. At least two lines / strips 3 which are directly fixed to the robot leg 5 at a distance A in the radial direction from the axis of the rotary output shaft 2 or fixed via an elastically deformable linear motion body 4 Consists of The elastically deformable linear motion body 4 softens the impact, prevents the wire / strip 3 from being cut, and enables detection of force as necessary. At least two wires / stripes 3 are twisted by the rotation of the drive motor 1, and a tensile force acts on the legs 6 or the linear motion body 4 to cause the joint to rotate.

  The feature of the leg joint drive device of the legged robot according to the present invention is that the joint of the leg of the robot and the drive motor can be separated as a drive system only by controlling the drive motor 1. When the rotational angle of the drive motor 1 is controlled to keep at least two wires / stripes 3 from being twisted, the joint 7 can move freely within the movable range. That is, the joint of the leg of the robot and the drive motor are separated as a drive system.

If the rotation angle α of the joint of the robot and the rotation angle α of the drive motor 1 are detected and the drive motor 1 is controlled using a computer CU equipped with an appropriate program, the joint can be made free as necessary. can do. Further, if a force detecting means such as a load cell is attached to the linear motion body 4, the joint drive torque can be detected and controlled.

This control system is shown in FIG. As shown in FIG. 3, the force F acting on the linear motion body 4 in the joint drive device, that is, the motion body that moves along the axial direction of the rotary motion output shaft 2, the rotation angle 117 </ b> A of the joint 7 , and the rotation of the drive motor 1. The angle α is detected, and the detection result is input to the control unit CU, and the rotation angle α and torque T of a given drive motor 1 are operated to give the joint 7 a desired rotation angle and rotation torque T. The amount is output from the drive motor 1. In FIG. 3, 113 is a wire-type drive device , and 117AS is a joint angle sensor.

An embodiment of a leg joint driving apparatus and control method for a legged robot according to the present invention will be described. FIG. 4 shows a case where one leg of a biped robot is taken as an example, and the leg joint driving device of the legged robot of the present invention is mounted on the hip joint 7. As shown in FIG. 4, by controlling the leg joint driving device of the legged robot of the present invention, the free leg can freely move without a clutch mechanism and the moment the leg changes from the supporting leg to the free leg. By temporarily applying torque to the joint, the free leg can be freely moved by its inertial force. Since the drive motor stops while the free leg moves freely, wasteful energy consumption can be avoided. In FIG. 4, T _M and θ _M are the torque and rotation angle of the drive motor, and T _H is the drive torque of the hip joint.

  The moment when the free leg comes into contact with the ground (referred to as “time point 1 when the supporting leg is switched to the free leg” in FIG. 4) is detected by using a detection means such as a contact switch on the sole or an adjacent sensor. If the knee is locked from the moment of detection, the knee is unlocked and a current is supplied to the drive motor 1 of the hip joint to apply torque to the hip joint 7. The motion of the free leg is detected by the angle sensor 117AS of the waist joint 7. When the target motion is reached, the drive of the free leg is terminated and the drive motor is returned to the initial position. From this point of time, if there is no need for disturbance compensation or change of stride, the drive motor 1 stops and the energy consumption of the drive motor 1 becomes zero until the next “time point 1 at which the support leg is switched to the free leg”. The robot performs passive walking. The other leg (shown by a broken line) shown in FIG. 4 is similarly driven and controlled to realize the simplest passive dynamic walking of the robot on a flat ground or a gentle slope.

With the leg driving method shown in FIG. 4, it is impossible to control the tilt (posture) of the robot body 5. Therefore, in order to perform the tilt control of the torso 5 and walking at the same time, the driving device of the present invention is attached to the front (F) and the rear (B) of the hip joint 7 of each leg. The tilt (posture) of the body 5 is controlled by the control of the front and rear drive motors 1. As shown in FIG. 5, for example, torque T _HL is applied to the hip joint 7 of the leg using a front drive motor L _HF for walking from the moment when the support leg (L) changes to a free leg. At the same time, the torso 5 tilts forward, and in order to control this tilt, torque T _HR in the opposite direction is applied to the hip joint using the drive motor R _HB behind the R leg that has changed to the support leg at the same time. Since this torque also supplies energy to the walking of the robot, the walking speed (step length) and the inclination (posture) of the trunk 5 can be controlled simultaneously by the two drive motors 1. Further, the leg joint driving device and control method thereof for the legged robot of the present invention can be applied regardless of the rotation method of the knee 7N or the realization of the expansion / contraction method as shown in FIG.

  Robots need to be able to walk not only on flat ground but also on floors with slight steps. In particular, when walking in a wasteland or going up and down stairs, it is essential to drive the knee joint 7N. Therefore, the apparatus of the present invention is also mounted on the knee joint 7N of the robot, and the knee joint 7N is actively controlled as necessary. Further, when it is not necessary to drive the knee joint 7N, the knee motor 7N is moved freely by returning the drive motor to the initial state. FIG. 7 shows a knee joint driving device and a leg of a robot equipped with the knee joint driving device.

Many conventional passive dynamic walking robots have a hard ankle and a circular sole. One of the reasons is to reduce the number of actuators as much as possible in order to realize energy-saving walking. Another reason is that the robot joint using the conventional driving technique is heavy and expensive. However, when the ankle is hardened, the robot's walking tends to become unstable, and the robot falls due to a slight step or disturbance.
By using the leg joint driving device of the present invention, it is possible to drive ankle joints that are light and inexpensive, and thus passive dynamic walking that is strong against steps and disturbances is possible. FIG. 8 shows a leg of a robot provided with the leg joint driving device of the present invention at the waist joint 7 and the ankle joint 7A according to this embodiment.

  By controlling the ankle and the hip joint 7, energy is supplied to the conventional passive walking robot that goes down a gentle slope through these two joints, realizing a more stable passive dynamic walking that can walk even on flat ground. To do. An effect equivalent to the inclination of the downhill is obtained by kicking the floor with the ankle 7A slightly before the moment of switching between the free leg and the supporting leg, and the step length and the inclination (posture) of the trunk 5 are controlled by driving the hip joint. . If it is flat, it is not necessary to drive the knee 7N, and stable and robust walking with less energy consumption can be realized. Further, in order to realize a lighter and cheaper ankle 7A, as shown in FIG. 9, only the rear driving device can be mounted and the front driving can be performed by the tension spring 8.

  In the case of the robot in the fourth embodiment in which the knee is not driven, it is impossible to ascend and descend the stairs. Thus, a high-performance robot capable of going up and down stairs also needs to drive the knee joint 7N. A robot leg that can drive or free all hip, knee and ankle joints is shown in FIG. Compared with the conventional robot leg drive system, the number of drive motors is increased, but since a speed reduction mechanism such as a gear is not required, it is advantageous or equivalent in price. According to the leg joint driving device and the control method thereof according to the present invention, there is an excellent function that can easily separate the driving motor and the joint at each joint, which has been difficult in the past, as a driving system. Has an excellent advantage.

According to the leg joint drive device and control method for a legged robot according to the present invention, since there is no speed reduction mechanism such as a gear, walking with less energy consumption is possible. Furthermore, the ability to make the robot's joints free increases the safety against human injury even when humans and robots come into contact in unexpected situations, and the probability of preventing robot failure when the robot falls. Can increase. When humans and robots come into contact with each other in an unexpected situation, safety against human harm can be increased, and even when a robot falls, the probability of preventing robot failure can be increased.

The perspective view which shows the basic form of the joint drive system in the leg joint drive device of the leg type | formula robot of this invention (a) is a figure which shows a rotational motion-linear motion conversion mechanism, (b) is the rotational motion for joint drive-linear motion It is a figure which shows a conversion mechanism. Schematic diagram showing the leg joint drive device of the legged robot of the present invention 1 is a block diagram showing a control system of a leg joint drive device of a legged robot according to one embodiment of the present invention. The schematic diagram which shows the drive device control method of the hip joint in the leg joint drive device of the legged robot which concerns on one Example of this invention. FIG. 6 is a schematic diagram showing a method for simultaneously controlling walking and a posture of a torso in a leg joint driving device for a legged robot according to another embodiment of the present invention. FIG. 5 is a schematic diagram showing an application of a method for simultaneously controlling walking and torso posture when a knee joint expands and contracts in a leg joint driving device for a legged robot according to another embodiment of the present invention. The schematic diagram which shows the leg which applied the leg joint drive device of the leg type robot which concerns on the other Example of this invention to the waist joint and the knee joint. The schematic diagram which shows the leg which applied the leg joint drive device of the legged robot which concerns on the other Example of this invention to the waist joint and the ankle joint. FIG. 8 is a schematic diagram showing an embodiment in which the weight of the joint drive is reduced in the embodiment shown in FIG. The schematic diagram which shows the leg which applied the leg joint drive device of the legged robot which concerns on the other Example of this invention to the hip joint knee joint and the ankle joint.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive motor 2 Rotation motion output shaft 3 Line | wire / strip | line 4 Linear motion body 5 Torso 6 Leg 7 Joint 11 Drive motor 12 Rotation motion output shaft 13 Line | wire / strip | line 14 Linear motion body 17 Joint A Line | wire and strip fixed end in a linear motion body Separation distance

Claims (3)

The rotational motion of the moving body that fixes at least one end of at least two lines / strips to the axial center of the rotary motion output shaft end and moves the other end of the wire / strip along the rotational motion output axis direction fixed with a symmetrical about the axis of the output shaft at a site spaced apart a predetermined distance a from the axis, also the predetermined distance a, the length L of the line-Article radius R of the wire-strip, said rotating A parameter that regulates the relationship between the torque T of the drive motor and the tensile force F that displaces the moving body in the direction of the rotary motion output shaft while the rotational angle α of the motion output shaft is used as a parameter of the motion displacement amount x of the moving body. The rotation of the rotary motion output shaft causes the at least two lines / stripes to be twisted to convert the rotational motion of the rotary motion output shaft into the displacement of the moving body that performs the motion along the direction of the rotational motion output shaft. , In addition, the exercise A leg is characterized in that a movement conversion device configured to convert the displacement of the movement into a rotary movement of the rotary movement output shaft is attached to at least one of a hip joint, a knee joint, and an ankle joint of a legged robot. -Type robot leg joint drive device. Fix one end of at least two wires / strips to the shaft center of the rotary motion output shaft end,
The other end of the wire / strip is fixed to a portion of the moving body that moves along the direction of the rotary motion output axis, symmetrical with respect to the axis of the rotary motion output shaft and separated from the axis by a predetermined distance A,
The predetermined distance A, the length L of the wire / strip, the radius R of the wire / strip, and the rotation angle α of the rotary motion output shaft are used as parameters of the motion displacement amount x of the moving body and the torque T of the drive motor. As a parameter governing the relationship between the tension force F that displaces the moving body in the direction of the rotary motion output axis,
Causing the at least two wires / strips to twist by rotation of the rotary motion output shaft;
The rotary motion of the rotary motion output shaft is converted into the displacement of a moving body that moves along the direction of the rotary motion output axis, and the displacement of the mobile body is converted into the rotational motion of the rotary motion output shaft. The motion conversion device is attached to at least one of a hip joint, a knee joint, and an ankle joint of a legged robot,
The motion conversion device detects at least one of the tensile force F and the rotation angle of the attached joint , and based on the detection result, the tensile force F and / or the rotation angle of the attached joint . A method for controlling a leg joint drive device of a legged robot, wherein either or both of the rotation angle α and the torque T are controlled so that a desired control amount is obtained. With leg joint drive device of the legged robot according to claim 1, as the rotary motion output shaft the mating attachment joint and the drive motor rotation angle in a state where no crowded twisting Clause the line-of drive system Create a separated state, let the legged robot perform passive walking ,
The legged torque to the mating attachment joint by the drive motor only in a predetermined range of the walking cycle of the robot added, tighten performed passive dynamic walking to the legged robot, further,
The method of the leg joint driving device of a legged robot, characterized in that, which accounts made active walking the mating attachment joint and the drive motor as a coupling state as the driving system via the Article the line-.

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