JP2592607B2 - Gait control method for quadruped walking machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a stable four-legged walking machine used as an extreme work robot for working in a nuclear reactor or a material transport robot in agriculture, fisheries, etc. The present invention relates to a control method for causing a user to walk in a state, and in particular, for allowing a user to walk dynamically while maintaining balance.
The present invention relates to a dynamic gait of a four-legged walking machine, that is, a method of controlling a dynamic way of walking.

(Prior art) In general, wheels or crawlers developed therefrom are used for land movement. However, wheel-type walking vehicles and crawler-type traveling vehicles have irregular terrain such as a large uneven surface or a soft surface. It is difficult to cross. Walking machines are considered promising for such irregular terrain movement.
Among walking machines, a four-legged walking machine having four legs is considered to be the most practical because it does not fall even if walking fails.

When such a four-legged walking machine performs walking, a method of controlling a static stable gait in which one leg is returned while supporting the center of gravity of the torso with three legs has been quite considerable. Research and development have been done and are becoming apparent. However, in order to cause the four-legged walking machine to move at high speed, it is necessary to perform not only static walking but also dynamic walking.

That is, in a quadruped walking machine that takes a crawl gait which is generally said to be the most efficient and stable among quadruped walking exercises, the maximum speed at which the swing leg can be generated mechanically is given by V, equal return speed of the free leg is at its maximum speed V, moreover, if the width of the free leg of the vertical movement at full flat ground walking is considered zero, the moving speed V _G of the center of gravity, It is expressed as Here, β is the duty ratio, that is, the ratio of the contact time during one cycle of movement of the leg.

As is apparent from this equation, when the slide into smaller beta centroid moving speed V _G increases, when beta = 0.5, center of gravity moving speed V _G is coincident with the V, so that the maximum speed is obtained . In this case, when β ≧ 0.75, three of the four legs are always in contact with the ground, so that static stable walking can be performed. However, when β <0.75, only two legs are in contact with the ground, that is, 2
The leg support phase will always be included in the walking cycle.

As described above, in order to cause the quadruped walking machine to perform high-speed movement, it is necessary to perform dynamic walking including the biped support phase. Therefore, control is required to maintain the dynamic stability even in the two-leg support phase.

Conventionally, when attempting to exercise while maintaining dynamic stability, conventionally, the dynamics of the motion system, that is, dynamic analysis, is used to determine a motion trajectory or joint torque that satisfies the stability condition, and is calculated. The torso was moved based on the exercise plan.

(Problems to be Solved by the Invention) However, the dynamics of the system are not always completely predicted. For example, during exercise, the friction conditions of the joints and the like vary considerably. In addition, there is a change in the position of the center of gravity due to the movement of passengers or cargo, the increase and decrease of fuel, and the like. Further, the impact force at the time of landing on the leg greatly varies depending on the state of the ground. Such fluctuations cannot be reliably predicted.

These friction conditions, the position of the center of gravity, the impact force from the ground, and the like greatly affect the calculation of the dynamics of the system. Therefore, unless these are accurately determined, a reliable torso motion plan cannot be made.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a quadruped walking machine with a stable dynamic operation that is less affected by fluctuations in the walking environment and characteristics of the walking machine itself. It is to be able to perform a gait.

(Means for Solving the Problems) In order to achieve this object, the present invention calculates the dynamic gait parameters in advance by calculating the dynamics of the motion system of the quadruped walking machine, Walking is actually performed based on the parameters, and the gait parameters are corrected by trial and error while maintaining the walking. Specifically, during walking, the landing timing of the return leg is obtained, and when the timing is shifted from the expected timing, the gait parameters are corrected so that the center of gravity is shifted in a direction in which the shift converges.

(Operation) With this configuration, when the walking motion deviates from the desired gait pattern during walking, the gait parameters for the next walking motion are corrected, and the corrected gait parameters are used. , The next walking motion is performed.
Therefore, the walking motion converges on the planned gait pattern. Since the gait parameters are corrected in a manner that also includes variations in the walking environment and characteristics of the walking machine itself during actual walking, the gaits are less affected by those variations. It will be.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, FIG. 1 shows a control method according to the present invention.
FIG. 2 is a perspective view schematically showing an example of a foot walking machine, and FIG. 2 is an explanatory diagram showing a trot gait which is a gait pattern of the quadruped walking machine.

As is apparent from FIG. 1, the four-legged walking machine includes four legs 1, 2, 3, and 4, and a body 5 supported by the legs 1-4. The legs 1 to 4 are configured to be able to bend and extend in the front-rear direction with respect to the body 5 by a pantograph mechanism or the like.

When such a four-legged walking machine takes a trot gait, first, as shown in FIG. 2 (A), from the state where all four legs 1 to 4 have landed, FIG. B)
The first leg 1 is moved forward in the traveling direction as shown in FIG. Then, as shown in FIG. 3C, before the first leg 1 comes into contact with the ground, the third leg 3 at a diagonal position to the first leg 1 is idled and returned. FIG. 2 (D) shows a state where the first leg 1 has landed and the third leg 3 is returning. When the third leg 3 lands, all the legs 1 to 4 land as shown in FIG. During this time, the center of gravity G of the body gradually moves forward due to the bending and stretching of the legs 1-4.

Subsequently, the second leg 4 and the fourth leg 4 are similarly moved.
By repeating the movement of the legs 1 to 4 in this way, walking is performed, and the torso moves forward.

By the way, in such a gait pattern, at least three legs are landing between FIGS. 2A and 2B and between FIGS. 2D and 2E. That is, it is in a state of static stable walking. However, in the section from the start of the return of the third leg 3 in FIG. 6B to the contact of the first leg 1 in FIG.
Is a bipod support phase supported only by diagonal bipods 2,4. Therefore, in that section, it is necessary to dynamically maintain stability.

In that case, the quadruped walking machine has a great advantage that it does not fall over even if the balance is lost. That is, considering the state of FIG. 2 (C), the body has two legs.
It is unstable because it is supported only by 2,4,
Since the first leg 1 and the third leg 3 in the returning state are returning slightly below the ground, even if they start to fall, if they try to fall forward, the first leg 1 and the rear will fall again. In this case, the third legs 3 respectively come into contact with the ground and support the body. Therefore, it does not fall down completely and the standing state is maintained. Thereby, walking can be started again from that state.

Further, in a quadruped walking machine, although a complicated three-dimensional movement is performed, there is an advantage that the falling mode is limited to only two types. That is, the statically unstable second
Even in the state shown in FIG. (C), the torso is supported by the two legs 2, 4, and when the body falls, the two legs 2, 4 are used.
A flat inverted pendulum-like motion around a straight line connecting the landing points is made. Therefore, the degree of freedom of the movement is 1, and only a two-mode falling state of falling in the direction of the front leg 1 or falling in the direction of the rear leg 3 occurs. And
The front leg 1 lands when falling forward, and the rear leg 3 lands before the target landing position when falling backward. Therefore, the falling state can be easily grasped.

By utilizing such characteristics of the four-legged walking machine, it is possible to correct the gait parameters while actually walking.

That is, according to the present invention, first, gait parameters that are considered to be capable of dynamically and stably walking are calculated in advance based on the dynamics of the motion system of the four-legged walking machine. Then, according to the exercise plan based on the gait parameters, the walking as shown in FIGS. 2A to 2E is executed.

In this case, the dynamics of the system are not perfect, and the balance may be lost in the state of FIG. 2 (C).
For example, if the center of gravity G moves too fast, the torso tends to fall forward in the process of shifting from FIG. 2 (C) to FIG. 2 (D), and the front leg 1 lands earlier than expected. Also, if the moving speed of the center of gravity G is too slow, the trunk tries to fall backward,
Hind leg 3 lands earlier than expected. Therefore, by determining such landing timings of the return legs 1 and 3, it can be easily determined whether or not the dynamic gait pattern at that time is normal.

And when the front leg 1 lands earlier than expected,
The gait parameters are switched such that the center of gravity G is located further rearward at the moment of the two-leg support phase in which the torso is supported by diagonal two-legs 2,4. When the rear leg 3 lands earlier than expected, the gait parameters are switched so that the center of gravity G is located further forward at the moment of the two-leg support phase.

Therefore, in the next walking cycle, walking is performed based on the corrected gait parameters. At this time, if the front leg 1 or the rear leg 3 still lands earlier than expected, similar gait parameters are adjusted again. The adjustment amount is set to be smaller than the previous adjustment amount.

By repeating the correction of the gait parameters in this way, the actual walking motion converges on the desired gait pattern, and stable dynamic walking can be performed.

During this time, the correction of the gait parameters is very simple because the center of gravity G is simply moved back and forth.

To move the center of gravity G back and forth, for example, as shown in FIG. 3, the calculated movable range P defined by the software of the support legs 2 and 4 is changed to the movable range Q determined mechanically.
Apart from that, it may be set narrower. In this case, for example, when it is desired to move the center of gravity G forward, the movable range P on the software is shifted rearward as shown in FIGS. Can be performed.

In addition, if the walking machine is configured such that the rear leg 3 returns to the ground by slightly pressing the ground when it returns, that is, if the leg 3 is kicked, the strength of the kick is adjusted. Accordingly, the position of the center of gravity G can be moved back and forth.

In any case, the position of the center of gravity G can be adjusted extremely easily.

In this way, since this control method is to actually make the four-legged walking machine walk and correct the gait parameters by trial and error during the walking, there is no need to find the exact dynamics. It is not affected by the fluctuation of the characteristics of the walking machine itself or the fluctuation of the walking environment.
Moreover, since it is only necessary to introduce a simple algorithm for switching the gait parameters in accordance with the landing timing of the return leg, the control system can be configured at low cost.

In the above embodiment, the four-legged walking machine assumes a trot gait. However, the present invention is not limited to this, and as shown in FIG. The return leg is used, and the other two legs 3, 4 are used as support legs. The present invention can also be applied to a four-legged walking machine that takes a pace gait. In that case, the center of gravity is moved to the right little by little because if it is moved too much to the center of gravity in the state shown in FIG. Then, the algorithm may be changed so that the center of gravity is not moved to the right side, that is, the side that completely falls down, for a certain degree or more.

(Effect of the Invention) As is clear from the above description, according to the present invention, 4
The gait parameters are adjusted during the walk by adjusting the gait parameters during the walk, and the gait parameters are searched for by trial and error. Gait can be realized. Moreover, the gait is a characteristic change of the walking machine itself such as a change in friction conditions at the joints of the legs, a change in the center of gravity due to an increase or decrease in fuel, or a change in the walking environment such as a ground state where the legs touch the ground. It will be less affected by

Therefore, it is possible to cause the four-legged walking machine to perform dynamic walking and increase the speed.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an example of a quadruped walking machine to which a control method according to the present invention is applied, FIG. 2 is an explanatory diagram showing a gait pattern of the quadruped walking machine, FIG. Is an explanatory view showing an example of a method of moving the center of gravity applied to the control method. FIG. 4 is a schematic perspective view showing another example of a quadruped walking machine to which the control method according to the present invention is applied. 1,2,3,4 ... legs, 5 ... body G ... center of gravity

Claims (1)

(57) [Claims] 1. A control method for causing a quadruped walking machine to walk while maintaining a dynamic balance; maintaining a dynamic balance by dynamically analyzing a motion system of the quadruped walking machine. Gait parameters are predicted and calculated, and walking is performed based on the calculated gait parameters. During the walking, the landing timing of the return leg is obtained, and when the timing deviates from the expected timing. Correcting the gait parameter so as to shift the center of gravity in a direction in which the deviation converges, wherein the gait parameter is corrected.