JPS61139567A - Walking machine - Google Patents

Abstract

PURPOSE:To enhance the control ability of a walking machine having a plurality of legs, by providing a resilient member for generating a force balancing a load exerted to each leg by its weight, to each leg so that no large force is required to be generated for supporting the weight of each leg. CONSTITUTION:In a joint type four-leg walking machine having each leg with three dimensional freedom, each leg is composed of upper and lower leg parts 5, 6, the upper leg part 6 being journalled at its base to each of four corners of a body 1 through the inermediary of a fork horizontal rotary shaft 2 and a fork horizontal vertical shaft 4. Further, the base of the lower leg part 6 is journalled to free end of the upper leg part 6 through a knee rotary shaft 4. In this arrangement the upper and lower forks 5, 6 are rotatably coupled together through a bearing 10. A spring 11 is attached at both ends to the upper and lower leg parts 5, 6 by means of spring fixtures 12. Further, the load exerted to the leg by the weight of the leg itself is compensated in its enitirety or in part by the force of the spring 11.

Description

[Detailed Description of the Invention] <Industry> Field of Application The present invention relates to a walking machine and is intended to eliminate control errors due to weight.

<Prior art and its problems> In recent years, walking machines with multiple legs have been developed. FIG. 1 shows an example of an articulated four-legged walking machine in which each leg has three degrees of freedom. In Fig. 1, 1 is the main body, 2 is the crotch horizontal rotation axis,
3 is the vertical axis of rotation of the crotch, 4 is the axis of rotation of eyes, 5 is the upper thigh, and 6 is the lower leg. Also θ1. θ2. θ3 is each rotation axis 2, 3°4
This is the rotation angle of , or the joint angle. In this walking machine, each axis of rotation 2, 3.4 of the legs has the weight of the main body of the walking machine, the weight of the two legs, and the inertia.

Although external disturbances such as load and friction are added, the influence of the own weight of the main body 1 is the greatest and this is the largest cause of error. The reason for this is that the characteristics of the DC motor that drives the rotating shafts 2 and 3.4 are as follows: Torque (T) - Rotation speed (N)
The same command value (voltage V) -
(This is because even if there is 1', the speed (rotational speed N) will change if the load (torque T) differs. In order to solve this problem, as shown in Figure 3, the target value and It is sufficient to reduce the output by giving an output corresponding to the deviation △X (position deviation in case of position control) from the current value. If the torque fluctuates widely and the relationship is random, in order to perform highly accurate control, it is necessary to change the gain l in the above formula in a complicated manner. Therefore, it is necessary to develop a control method, which also increases calculation time (CPU time) and requires a great deal of effort.

In conventional walking machines that use position control or speed control for walking, attempts have been made to eliminate control errors caused by self-weight by improving servo rigidity, but satisfactory results have not been obtained.

The reason for this will be explained with reference to FIG.

Note that in this explanation, the magnitude of servo rigidity corresponds to the magnitude of mechanical rigidity, so the explanation will be made using mechanical rigidity to facilitate understanding.

When actually controlling the legs, there are always errors in the trajectory, and the ground surface is uneven. In this case, as shown in the front view in FIG. 4 1al, the main body 1 and the legs 1', 12, 13
．． Assuming that 14 is a completely rigid body, if a position error of even 1 μl occurs, the three legs 1. ．． 12
, 13 are in contact with the ground, and the legs 44 are floating. P#14
When the body 1 floats, the load applied to the leg 12 diagonally to the leg 1!4 decreases, as shown in the plan view of FIG. ．． It will be supported by 13. Furthermore, when walking over an obstacle, as shown in Figure 4 (C1) shown in the plan view, when leg e4 floats, leg e
The load on leg 1.2 is lighter, with leg 1.1 carrying most of the load, and furthermore, the asymmetry causes the load on leg 13 to be extremely high. If the load applied to each leg is different in this way, as already explained with reference to FIG. 2, the control by the DC motor that drives the rotating shaft of each leg will be disrupted, and a vibration phenomenon will occur. In the end, increasing the servo rigidity not only has the disadvantage that the legs float, but also causes vibration phenomena in some cases.

In order to solve the unbalance of the load on the legs due to restraints caused by control errors and the weight of the walking machine, there is a method of reducing the stiffness of the legs and actively using compliance.

With this method, even if the position is slightly deviated, the resulting spring reaction force is small, so the restraining force on the legs is reduced and the legs do not lift up. However, as shown in the front view in FIG. 4(d), the leg l.

12) If the leg 13 is raised while the I13 and 14 are on the ground, the load distribution will change, and the leg 14 with the larger load will bend, causing the walking machine to move in an unstable direction as shown by the arrow in the figure. lean towards. This phenomenon is particularly noticeable when the center of gravity is high.

On the other hand, in a walking machine that uses force control to walk, lifting of the legs is less likely to occur, but without sufficient conoplasty, it is difficult to detect force with high reliability and accuracy, and stable control cannot be achieved for practical use. It didn't reach that point.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, it is an object of the present invention to provide a walking machine that can perform highly accurate control and operate stably and efficiently.

Means for Solving the Problems> The present invention achieves the above object by providing a walking machine with a plurality of legs, in which each leg is provided with an elastic body that generates a force that balances the load applied to each leg due to its own weight. It is characterized by being equipped.

<Function> Part of the self-weight support force, which is one of the largest forces generated when walking, can be borne by elastic bodies such as springs, rubber, and shape memory alloys, which have a simple structure, are lightweight, and are inexpensive, and actuators are generated. This reduces the force that must be applied and improves controllability.

Embodiments The present invention will be explained using an example of a four-legged, three-jointed walking machine shown in FIG. X in the front/back, left/right, and up/down directions on the walking machine
, take the y and Z axes.

When the inclination of the walking machine is small, its own weight is only in the Z-axis direction. If the main body 1 is tilted significantly, the X component and the X component of its own weight can be easily calculated by measuring the tilt angle using a tilt sensor or visually. The joint angle of the leg is θ1, θ2) θ3
These can be measured using encoders, potentiometers, etc., and the position of the grounding point of the leg tip can also be easily calculated. The load applied to each rotating shaft 2.3.4 due to its own weight can be calculated from the following equation based on the position of the center of gravity, the inclination, and the position of the tip of the leg.

t=, l-f However, [: does not represent the torque due to the load applied to 3 joints, vector 1: represents the force applied to one leg due to its own weight. In the invention, the self-weight compensation torque 9 obtained by the above formula is generated on each rotating shaft 2.3.4 by an elastic body to be described later.For this reason,
There is a balance between the load applied to each rotating shaft 2.3.4 due to its own weight and the self-weight compensation 1~l. As a result, the actuator that performs position control or speed control only needs to generate force for controlling the position or speed, and can perform highly accurate control.

In addition, when you stop after walking according to a movement command, if your legs try to leave the ground due to an error, the elastic body's own weight compensation 1 - Luk 6 moves your legs in the direction of touching the ground, preventing them from lifting up. The legs share the required torque and stand still in a stable state. On the other hand, when walking by giving a movement command, the self-weight and self-weight compensation torque t are in balance, so the influence of the self-weight disappears, and each leg becomes a heavy load with no load, resulting in extremely stable motion l'. This enables smooth position tracking and synchronization of each leg.

Here, a specific example of the present invention will be explained with reference to the axis of rotation. As shown in FIG. 5, the upper leg 5 and lower leg 6 are rotatably connected to each other by a bearing 10 in the eye roll shaft 4, and is driven by an actuator (DC motor) provided within the bearing 10. One end of the spring 11 is fixed to the upper leg 5 by a spring fixture 12, and the other end is fixed to the lower leg 6. All or part of this spring 11 can therefore be compensated. This effect is effective when the motion range of the legs is not very large and the direction of the force applied to the legs due to its own weight does not change drastically. In this case, the compensating force by the a1 spring 11 does not necessarily have to be the same as the load due to its own weight, and may be larger than this. In short, the actuator (motor)
If even a part of the self-weight (self-weight) and the torque applied to the actuator can be compensated on an average basis, the power borne by the actuator will be reduced, saving labor and making it possible to move even further. To explain a specific example, when there is a change in force due to its own weight as shown in Fig. 6 [al], if the self-weight compensation force is given, the force actually output by the actuator will be as shown in Fig. 6 (bl). As in, less is better.

As the elastic body that generates the compensating force, in addition to springs and Goya, shape memory alloys (superelastic alloys) can be used. As shown in Figure 7, shape memory alloys have a constant elastic force when the displacement exceeds a certain value, so depending on the operating angle of the legs, they may be more effective than springs or combs.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, since the actuator is provided with an elastic body that generates a force that balances the load, it is not necessary for the actuator to generate a large force to support its own weight. This improves controllability. Furthermore, in the present invention, by using a lightweight and inexpensive elastic body, lifting can be prevented and smooth walking can be achieved.

The control method of the present invention is applicable to walking machines in general, and is particularly applicable to the robot robot 1-(
It is useful for application to C/V Rohot), Rohot 1-1 small inspection robot for nuclear reactors for extreme work, and nuclear reactor transfer port hot.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a four-legged, three-jointed walking machine, Figure 2 is a characteristic diagram showing the characteristics of a DC motor, Figure 3 is a characteristic diagram showing gain characteristics, and Figure 4 is a conventional walking machine walking machine. This is to explain the condition, Figure 4 1a) ldl is the front view,
Figure tb+ (C) is a plan view. FIG. 5 is a block diagram showing a fourth embodiment of the present invention, and FIG. 6 (a
+, (b) is a characteristic diagram showing the relationship between the forces applied to the legs, and FIG. 7 is a characteristic diagram showing the spring characteristics of the elastic body. In the drawing, 1 is the main body, 2 is the horizontal rotation axis of the crotch, 3 is the vertical rotation axis of the crotch, 4 is the rotation axis of the thigh, 5 is the upper leg, 6 is the lower leg, 10 is the actuator), 11 is the spring, and 12 is the spring fixing device. , 1,, 12', J3. 14 is a leg. 41 (a)
(b)(c)
(d) Figure 5 Figure 6 (a) (b)
. Figure 7 4 standing (angle)

Claims (2)

[Claims] (1) A walking machine having a plurality of legs, characterized in that each leg is provided with an elastic body that generates a force that balances the load applied to each leg due to its own weight. (2) A walking machine according to claim 1, wherein the elastic body is a shape memory alloy.