JPS61134805A - Controlling method of walking machine - Google Patents

Abstract

PURPOSE:To prevent floating-up, and to make walking smooth by adding a force control to a position control or a speed control. CONSTITUTION:A four leg and three joint type walking machine is formed by a body 1, a groin horizontal revolving shaft 2, a groin vertical revolving shaft 3, a knee revolving shaft 4, legs of a thigh 5 and a crural part 6, etc., and these legs are walked. In this case, when (x)-(y) axes are set in front and rear, right and left, and upper and lower directions of the walking machine, in case when an inclination of the walking machine is small, the empty weight is in only the Z axis direction and in case when its inclination is large, (x)-(y) components of the empty weight are calculated by measuring an inclination angle by an inclination sensor and a visual sense, etc. A load applied to each revolving shaft 2-4 is derived by the empty weight from these position of the center of gravity, inclination,and leg tip position, and force control flor generating a force which is balanced to this calculated load, in each revolving shaft 2-4 is executed. In this way, it will suffice that a position control system or a speed control system generates only a force for controlling a position and a speed, and the control can be executed with a high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Minute Hand> The present invention relates to a method of controlling 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 a hip vertical rotation axis, 4 is a knee rotation axis, 5 is an upper leg, and 6 is a lower leg. Also θ,, θ2. θ3 is the rotation angle of each rotating shaft 2, 3°4, that is, the joint angle. In this walking machine, each rotation axis 2, 3.4 of the leg has the weight 2 of the main body 1 of the walking machine.
Weight of the legs, 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, 3, and 4 are as follows: torque (T) - rotation speed (N) as shown in Figure 2.
As shown in the characteristics, even if the command value (voltage V) is the same, if the load (torque T) increases, the speed (rotational speed N) will change.
This is because it will change. In order to solve this problem, as shown in Fig. 3, the output V according to the deviation ΔX (position WII difference in the case of position control) between the target value and the current value
= may be controlled by giving ΔX (where k is the gain). However, if the torque applied to the motor fluctuates significantly and the relationship is random, in order to perform highly accurate control, it is necessary to use the gain k in the above formula.
If it becomes necessary to make complicated changes and the number of rotating axes increases, a new control method must be developed, 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(a), the main body 1 and the legs j, 12. j3
．． Assuming that 14 is a completely rigid body, if a position error occurs even in one voice, the three legs 1. ．． 12.
Only leg 13 touches the ground, and leg I4 floats. When the leg 14 floats, the load applied to the leg 12 diagonally to the leg 14 also decreases, as shown in FIG.
Main body 1 is mostly legs 1. ．． It will be supported by i3.

Furthermore, when walking over an obstacle, as shown in Figure 4 (01) shown in the plan view, when leg 14 floats, the load on leg 12 becomes lighter, and legs 1, 13 support most of the load. , furthermore, since it is asymmetrical, the load applied to the legs 13 becomes extremely large.If the loads applied to each leg are different in this way, as already explained based on FIG. The control is disturbed and a vibration phenomenon occurs.In the end, increasing the servo rigidity not only causes the disadvantage 1 that the legs float, but also causes a vibration phenomenon 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.

In this method, even if the position is slightly deviated, the resulting spring reaction force is small, the restraint force on the leg is reduced, and the leg does not lift up. However, as shown in the front view in FIG. The walking machine tilts in an unstable direction as shown by the arrow in the figure.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 compliance, it is difficult to detect force with high reliability and precision, and stable control cannot be achieved, making it impractical. It didn't work out.

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

Means for Solving the Problems〉 The method of the present invention for achieving the above object is a walking machine that walks by controlling the position or speed of a plurality of legs. It is characterized by the addition of force control that calculates the load applied to the shaft and generates a force on each rotating shaft that is balanced against the calculated load.

<Function> In the present invention, stable operation is possible because the stable operation of position control and speed control is combined with the flexibility of force control. Furthermore, the self-weight compensation amount is set to an amount t! that is more appropriate than the position control gain or speed control gain. The system can also be stabilized by making it small.

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-rear direction, left-right direction, and downward direction 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 and Y components of its own weight can be easily calculated by measuring the tilt angle using a tilt sensor or visually. The joint angles of the legs are 01, 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=J-f However! : Vector f representing the torque due to the load applied to the three joints : Vector JT representing the force applied to one leg due to its own weight: Transformation matrix of 3×3 matrix In the method of the present invention, the self-weight compensation torque t obtained by the above formula is applied to each rotation axis 2. .3.4. Therefore, the load applied to each rotating shaft 2.3.4 due to its own weight and the self-weight compensation torque are balanced. As a result, the position control system or speed control system
It is only necessary to generate force to control the position or speed, and highly accurate control can be performed. 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 self-weight compensation torque number moves the legs in the direction of the ground, which prevents them from lifting up. It shares the torque and stands still in a stable state. On the other hand, when walking by giving a movement command,
Since the self-weight and self-weight compensation l and lukut are balanced, the influence of self-weight is reduced, and each leg is in a mode of heavy production without any load, allowing extremely stable position tracking and smooth synchronization of each leg. Ru.

Furthermore, according to the method of the present invention, as shown in FIG.
In other words, the operating point P is raised by the self-weight compensation torque t,=
Control can be performed in a stable region. Note that the shaded area in FIG. 5 is an unstable area due to friction and the like.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, since force control is added to position control or speed control, lifting can be prevented and smooth walking can be performed.

[Brief explanation of drawings]

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. It explains the condition, and Figure 4 (al (dl is the front view,
Figure (b) (C1 is a plan view. Figure 5 is a characteristic diagram showing the control area according to the present invention. In the figure, 1 is the main body, 2 is the crotch horizontal rotation axis, and 3 is the crotch vertical rotation axis) , 4 is the knee rotation axis, 5 is the upper leg, 6 is the lower leg, 11, j,, 13. j4 is the leg.

Claims (1)

[Claims] In a walking machine that walks by controlling the position or speed of multiple legs, the load on each axis of rotation of each leg is calculated from the load due to its own weight on each leg, and a force that is balanced against the calculated load is applied to each leg. A method for controlling a walking machine characterized by adding force control to be generated on a rotating shaft.