JPH04293687A - Walking robot - Google Patents

Abstract

PURPOSE:To determine the traveling attitude minimizing the torque applied to leg joint portions when a leg wheel type walking robot is horizontally traveled with wheels. CONSTITUTION:When a leg wheel type walking robot is horizontally traveled, the gravitational force mg and the inertial force ma are applied to a robot main body 7, and the excessive torque is applied to leg joint portions 8, 9. The angle of legs l, 2, 3, 4 is controlled in parallel with the resultant force direction of the gravitational force mg and the inertial force ma so that the torque applied to the joints 8, 9 is minimized in response to the walking speed (a) and the gravitational acceleration (g).

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a leg-wheel type walking robot having running wheels at the tips of its legs, and to a walking robot that controls the leg angle so as to reduce external force when running horizontally. be.

0002

2. Description of the Related Art As one of the moving devices capable of quickly moving over obstacles, there is a leg having a leg a and a running device such as a wheel b at its tip, as shown in FIG. There is a wheel-type moving device, that is, a leg-wheel type walking robot c. This device can quickly run on level ground, move on uneven ground, and straddle obstacles by running on wheels b, walking on legs a, or a combination thereof. As for how to control the legs of this walking robot when walking on uneven ground, various methods of controlling the legs have been studied, as shown in Figure 4, which shows various patterns of movement. (The pattern diagram of uneven ground walking shown in Figure 4 is extracted from the Journal of the Robotics Society of Japan, Volume 2, Issue 3)

0003

[Problems to be Solved by the Invention] However, in the past, walking robots have placed too much emphasis on walking on uneven ground using their legs, and insufficient consideration has been given to horizontal movement using wheels. For example, when the wheels at the end of the legs accelerate or decelerate horizontally, excessive torque may be applied to the motors that drive the leg joints, so a high-torque motor is required to drive the leg joints. However, the problem remains that the weight of the moving device inevitably increases.

0004

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a walking robot having an arbitrary number of legs having arbitrary degrees of freedom and running wheels at the tips of the legs. According to the gravitational acceleration, the leg angle is controlled in a direction in which torque applied to each joint of the leg is minimized.

[0005]

[Operation] When a leg-wheel type robot runs horizontally, gravity and inertia are applied to the robot body, and if the arm length is long, excessive torque is applied to the joints of the legs that support it. By controlling the posture of the legs to match the running acceleration and gravitational acceleration, the torque applied to the joints can be reduced. Therefore, the motor for driving the joints can be made smaller and lighter, and the weight of the robot can be reduced.

[0006]

Embodiment FIG. 1 shows a conceptual diagram of a walking robot according to an embodiment of the present invention. The four legs 1, 2, 3, and 4 are each 2
It has a degree of freedom. The figure is shown as viewed from the side in the running direction, so only one side is shown, but the other side is assumed to be in the same state. Each leg having two degrees of freedom consists of an upper link 5 and a lower link 6, which are rotatably connected at a middle joint 8, and the upper link 5 is rotatably connected to the robot body 7 at an upper joint 9. ing. Further, wheels 10 are rotatably attached to the lower end of the lower link 6, forming a leg-wheel type walking robot. Each joint 8
, 9 and the wheels 10 are equipped with joint drive motors (not shown), which freely drive the individual joints 8 and 9.
In addition to walking on uneven ground as shown in FIG. 4, the wheels 10 allow the robot to travel horizontally.

When the above-mentioned leg-wheel type walking robot runs horizontally, assuming that the mass of the robot is m, the running acceleration is a, and the gravitational acceleration is g, a resultant force of gravity mg and inertial force ma is applied to the robot body 7. The four legs 1 and 2 that support this
, 3 and 4 are subjected to a large load, which is applied to each joint 8 and 9.
is added as excessive torque. Therefore, in order to maintain the posture of each joint 8, 9, it is necessary to use a high-torque motor for each joint drive motor, which is higher than that required for driving the joints. This is accompanied by an increase in the overall weight of the walking robot, causing problems in various movements.

In this embodiment, when the wheels 10 are horizontally traveling, the upper link 5 and the lower link 6 are controlled to appropriate traveling angles in order to reduce the load torque on the joints 8 and 9 described above. That is, by setting the posture of each leg 1, 2, 3, and 4 parallel to the direction of the resultant force of gravity mg and inertia force ma as shown in the figure, the moment applied to the legs can be made zero. The joint angle θ of the upper link 5 at this time is as follows (
1) It can be obtained using the formula. θ=tan(a/g)……(1) For the lower link 6, if the straight line (indicated by a broken line) connecting the joint axis of the lower link 6 and the grounding point y of the wheel 10 is at an angle of θ, then Therefore, if the length of the lower link 6 is l and the radius of the wheel is r, θ' that satisfies the following equation (2) can be found, and θ' can be taken as the joint angle of the lower link 6. tanθ=a/g=lsinθ'/(
l cos θ′+r) (2) The above method for calculating leg posture can be applied to cases where an arbitrary number of legs and each leg have an arbitrary degree of freedom. Note that when the robot takes the running posture shown in FIG. 1, the running stability of the robot may deteriorate, but this can be resolved by controlling the joint angle of the upper link 5 to a leg posture that is θ+180°. That is, by adopting a crouching posture as shown in FIG. 2, the same effect as described above can be obtained, and stability can also be improved.

[0009]

Effects of the Invention As described above, according to the present invention, when a leg-wheel type walking robot runs horizontally, the leg angles are controlled to be in accordance with the running acceleration and the gravitational acceleration. Since the excessive torque applied to the parts can be reduced, the motors for driving the joints can be made as small and lightweight as necessary for driving the joints, making it possible to reduce the weight of the robot. It is more free and
It is demonstrated as an effect that allows for free movement.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a legged and wheeled robot according to an embodiment.

FIG. 2 is a conceptual diagram of the running posture of the same as above.

[Fig. 3] A schematic diagram of a conventional walking robot.

[Figure 4] Diagram of the uneven terrain running pattern of the walking robot.

[Explanation of symbols]

1, 2, 3, 4...legs 7...robot body 8...middle joint
9...Upper joint 10...Wheel
θ…Direction angle of resultant force of gravity and inertia force

Claims (1)

[Claims] [Claim 1] An arbitrary number of legs having arbitrary degrees of freedom;
In a walking robot having running wheels at the tips of its legs, when the walking robot moves horizontally using the running wheels, the leg angle is adjusted so that the torque applied to each joint of the leg is minimized depending on the running acceleration and the gravitational acceleration. A walking robot that is characterized by its posture control in the direction in which it moves.