JP3183557B2 - Walking control device for legged mobile robot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a walking control device for a legged mobile robot.

[0002]

2. Description of the Related Art Conventionally, wheel-type, crawler-type and leg-type robots have been proposed as technologies relating to mobile robots. Among them, as for the control technology of a legged mobile robot, the technology related to a one-legged robot (Raibert,
MH, Brown, Jr. HB, "Experiments in Balance With
a 2D One-Legged Hopping Machine ", ASME, J of DSM
C, vol. 106, pp. 75-81 (1984)), Technology on biped robots (Journal of the Robotics Society of Japan vol.l, no.3, pp.167-203,
1983) Technology related to four-legged robots (Journal of the Robotics Society of Japan vol.9, no.5, pp.638-643, 1991), technology related to six-legged robots (Fischeti, MA, "Robot Do the Dirty W"
ork, "IEEE, spectrum, vol.22.no.4, pp.65-72 (198
5). Shin-Min Song, Kenneth J. Waldron, "Machines T
hat Walk; The Adaptive Suspension Vehicle ", The MIT
Press Cambridge, Massachusetts, London. England)
Many have been proposed. Furthermore, a technology to generate a dynamic and stable movement (walking) pattern in real time with a relatively low degree of freedom robot (Shimoyama, "Dynamic walking of a stilt-type biped walking robot", Transactions of the Japan Society of Mechanical Engineers C) , Vol. 48, No. 4
Issue 33, pp. 1445-1454, 1982. and "Legged Robots on
Rough Terrain; Experiments in Adjusting Step Lengt
h ", by Jessica Hodgins. IEEE, 1988) and a technique for generating a stable movement (walking) pattern offline with a robot having relatively many degrees of freedom (JP-A-62-97006, JP-A-63-150)
No. 176) has also been proposed.

[0003]

By the way, in the above-described method for generating a stable off-line movement pattern, when the robot walks on a flat road, the foot is horizontal and the joint angle trajectory (walking) is stable mechanically. This can be realized by controlling the joint angle so as to follow the pattern). For example, if the user walks quietly, it is possible to stably walk by controlling the center of gravity trajectory to always be within the foot. In dynamic walking, the center of gravity trajectory may be controlled so that zmp is within the foot. However, the road surface on which the legged mobile robot moves is rarely strictly as designed, and irregularities and inclinations that are unexpected in a walking pattern often actually exist. When encountering such unevenness and inclination, the leg-type mobile robot may have an unstable posture because the foot angle of the supporting leg is inclined, and as a result, the center of gravity trajectory deviates from the target trajectory. The same is true for the method using the above-described method of generating a movement pattern in real time and walking, and such a disturbance is
This will cause you to lose your posture.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve stability in a mobile environment by always walking stably without losing posture even when unexpected road surface irregularities or slopes are encountered. To provide a walking control device for a legged mobile robot.

[0005]

Means for Solving the Problems In order to solve the above problems, the present invention has the following constitution. The sign to be described later
When subjected will be described, with the one of claims, the body (housing
Body) 24 and a walking control device of the legged mobile robot 1 having a plurality of legs (leg links 2).
Target position (target trajectory) of the specified part of the robot
The joints of the robot so that the predetermined portions match.
(10R (L)), the absolute angle of the upper body of the robot with respect to the direction of gravity {x, ψ
y and / or absolute angular velocity ψ dot x, ψ dot y detected
To that detection means (control unit 26, the inclination sensor 40),
The absolute angle and / or absolute angular velocity of the detected upper body
Based on the contact area of the robot (foot 22R (L))
Absolute angle qx, qy and / or absolute angle of
Estimating means for estimating angular velocity (control unit 26, block
Click B1), the absolute angle of the estimated ground site and / or
Is the target position for changing the target position based on the absolute angular velocity.
Position changing means (control unit 26, block B3) , and drive control of the joint according to the changed target position.
Drive control value calculating means (control unit 2) for calculating the control value
6, block B4), was configured with. Also,
In the second aspect, the predetermined portion is located at the center of gravity (C
x, Cy, Cz). Claims
In item 3, the absolute angle of the detected upper body and / or
Or, based on the absolute angular velocity, the joint closest to the contact area
(Ankle joint 18, 20R (L))
Correction (control unit 26, block B6)
did.

[0006]

When an unexpected irregularity or inclination of the road surface is encountered, the absolute angle (speed) of the robot's ground contact area with respect to the direction of gravity differs from the expected value, and the actual value of a predetermined part, for example, the center of gravity trajectory, is also set to the target value. Deviate from the value. Since the joint is estimated and controlled so as to coincide with the target value, the posture can be quickly recovered, the stable walking can be always performed, and the stepping ability in the moving environment is improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below, taking a bipedal walking robot as an example of a legged mobile robot. FIG. 1 is an explanatory skeleton diagram showing the robot 1 as a whole. The left and right leg links 2 are provided with six joints (for convenience of understanding, each joint is shown by an electric motor that drives it). . The six joints are, in order from the top, joints 10R, 10L (R on the right side, R,
Let L be the left side. Joints 12R and 12L in the roll direction of the hip (around the x axis), the joints 14R and 14L in the same pitch direction (around the y axis), and the joint 1 in the pitch direction of the knee.
6R, 16L, ankle pitch joints 18R, 18
L, joints 20R and 20L in the same roll direction,
Below that is a foot 22R provided with a spring mechanism described later,
22L is attached, and a casing (upper body) 2
The control unit 26 is stored in the control unit 4.

In the above, the hip joint is joint 10R (L),
12R (L) and 14R (L), and the ankle joint is composed of joints 18R (L) and 20R (L).
In addition, the thigh links 32R, 32 between the waist joint and the knee joint.
L, the lower leg links 34R, 34 between the knee joint and the ankle joint.
L connected. Here, the leg link 2 is given six degrees of freedom for each of the left and right feet, and by driving these 6 × 2 = 12 joints (axes) to appropriate angles during walking, the entire foot To a desired motion, and can be arbitrarily walked in a three-dimensional space. As described above, the above-mentioned joint is formed of an electric motor, and further includes a speed reducer for boosting the output thereof. Details of the joint are described in the application proposed by the present applicant (Japanese Patent Application No.
No. 324218, Japanese Patent Laid-Open No. 3-184787), and the like, which is not the subject of the present invention, and therefore, further description is omitted.

In the robot 1 shown in FIG. 1, a known six-axis force sensor 36 is provided at the ankle, and force components Fx, F in the x, y, and z directions transmitted to the robot through the foot.
y, Fz and moment components Mx, M around the direction
By measuring y and Mz, the presence or absence of landing on the foot and the magnitude and direction of the force applied to the supporting leg are detected. In addition, foot 22R
At the four corners of (L), a capacitance type ground switch 38 (FIG. 1)
(Not shown) is provided to detect the presence / absence of the touchdown of the foot. Further, a tilt sensor 40 is provided in the housing 24, and x
The tilt angular velocity with respect to the z-axis in the -z plane and the yz plane, that is, with respect to the direction of gravity is detected. The electric motor of each joint is provided with a rotary encoder for detecting the amount of rotation. Further, although omitted in FIG.
At an appropriate position, an origin switch 42 for correcting the output of the inclination sensor 40 and a limit switch 44 for fail countermeasures are provided. These outputs are output from the housing 2 described above.
4 is sent to the control unit 26.

FIG. 2 is a block diagram showing the details of the control unit 26, which comprises a microcomputer. The output of the tilt sensor 40 and the like is converted into a digital value by the A / D converter 50, and the output is
Via the RAM 54. The output of an encoder disposed adjacent to each electric motor is input to the RAM 54 via a counter 56, and the ground switch 3
Outputs of the RAM 8 and the like are similarly sent to the RAM 5
4 is stored. The control unit includes first and second arithmetic units 60 and 62 each including a CPU. The first arithmetic unit 60 reads a predetermined walking pattern such as a center of gravity trajectory stored in the ROM 64. Then, the target joint angle is calculated and transmitted to the RAM 54. Further, the second arithmetic unit 62 reads the target value and the detected actual value from the RAM 54 as described later, calculates a control value necessary for driving each joint, and outputs the control value via the D / A converter 66 and the servo amplifier. Output to the electric motor that drives each joint.

Next, the operation of the control device will be described.

FIG. 3 is a block diagram showing control when the robot 1 is tilted in the front-rear direction. Although not shown, the control described below is exactly the same in the left-right direction. If the inclination angle is sufficiently small, it is possible to separate the three-dimensional tilts toward the tilt angles of the right and left front and rear, it will be used to coordinate transformation of a large listen lever 3D. Here, for the sake of simplicity, a case where the inclination angle is sufficiently small will be described. In FIG. 3, the absolute coordinates fixed to the road surface are defined as XYZ coordinates,
The coordinates fixed to the back surface of 2R (L) are represented by the internal coordinates xy-
Let it be the z coordinate. The preset walking parameters (trajectory parameters) are the position of the center of gravity, the speed of the center of gravity, the foot position, and the foot speed.

Now, the foot of the robot 1, for example, the right foot 2
It is assumed that the 2R is inclined as shown by a solid line in FIG. 3 due to stepping on a slope or unevenness (a broken line indicates a target posture).
At this time, for example, in the case of quiet walking, the center of gravity trajectory is
There is a risk of falling out of R and falling. However, if the position of the center of gravity is at the target position indicated by the broken line with respect to the absolute coordinates XYZ that are fixed on the road surface, the vehicle will not fall.

Therefore, in this control, the block B1
Is used to estimate the angles qx, qy of the foot 22R. That is, the inclination angle velocities ψdot x and ψdot y (absolute angles with respect to the direction of gravity; suffixes indicate directions; the same applies hereinafter) of the housing 24 are detected through the above-described inclination sensor 40, and the detected values are integrated to obtain the inclination angle 傾斜 x. , Ψy, and from the obtained inclination angle and the joint angle θn (relative angle between the links) detected through the rotary encoder, the angle qx,
qy (absolute angle to the direction of gravity; the subscript indicates the direction)
Is estimated. The joint angle θ is the angle of the twelve joints shown in FIG. 1, and the subscript n indicates the corresponding joint.

Next, in block B2, if the estimated value has a high-frequency vibration, the robot causes hunting due to a feedback loop. Therefore, a low-pass filter is provided to remove only the low-frequency components of the foot angles qx and qy. To detect.

Next, in block B3, the foot angle q
Using x and qy, as shown in the figure, the position of the center of gravity with respect to the absolute coordinates XYZ is determined by the internal coordinates xy fixed to the robot.
Convert to -z. That is, the center-of-gravity trajectory in the absolute coordinate system is converted into the center-of-gravity trajectory as viewed from the internal coordinate system fixed to the robot.

Next, in block B4, based on the converted center-of-gravity trajectory, the so-called inverse kinematics problem is solved as shown to calculate the angles of the twelve joints.

Next, in block B5, as described above with reference to FIG. 2, the center-of-gravity trajectory is output to the position servo system for controlling the joint angle so that the robot 1 recovers to the desired posture indicated by the broken line. Control.

In block B6, the detected inclination angular velocity is approximated to the center of gravity velocity, and the ankles 18, 20R (L)
Only feedback control is performed to improve stability. That is, it is originally desirable to control not only the position of the center of gravity but also the velocity of the center of gravity, but such tilt feedback control is locally performed to simplify the calculation.
Note that this tilt feedback control is performed by adding the gains Kx, K to the detected tilt angular velocity ψdot x, ψdot y.
The value obtained by multiplying y is added to the angle of the ankle joint 18, 20R (L) (calculated in block B4).

In this embodiment, as described above, when the foot angle is a flat road (zero angle), even if an unexpected inclination occurs due to stepping on a slope or unevenness, the foot sensor is attached to the housing. The angle is estimated, coordinate transformation is performed using the estimated foot angle, and the joint angle is controlled so that the center of gravity trajectory does not deviate from the absolute coordinates fixed on the road surface. And a stable posture can be maintained.

Although an example in which all twelve joints are controlled has been described above, the number of joints may be reduced to reduce the calculation load.

In the above, among the predetermined trajectory parameters of the center of gravity position, the center of gravity speed, the foot position, and the foot speed, only the center of gravity position (center of gravity trajectory) is controlled to a target value in accordance with the foot inclination angle. Although an example is shown, as described at the end of the first embodiment, the center of gravity speed may be controlled, and further, the foot position and speed may be controlled. Further, the position is not limited thereto, and a position such as a waist position that is easily obtained as compared with the center of gravity position may be used.

In the above description, the inclination angle of the foot is estimated, but the inclination angular velocity may be estimated.

Further, an example has been shown in which the feedback control to the ankle joint is also performed in the block B6, but may be omitted when the walking speed is low.

Further, in the above description, the case where the walking pattern (trajectory parameter) is set in advance is taken as an example.
The present invention is not limited to this, and may be applied to a technique for obtaining a walking parameter in real time during walking.

Further, in the above description, a bipedal walking legged mobile robot has been described as an example. However, the present invention is not limited to this, and is applicable to a legged mobile robot having three or more legs.

[0027]

[Effect of the Invention] According to claim 1, wherein, met walk controller of a legged mobile robot having a body and a plurality of legs
A predetermined target position of a predetermined part of the robot.
The joints of the robot so that the predetermined portions match.
In which drives and controls the absolute angle and / or <br/> Ru detecting means to detect an absolute angular velocity with respect to the direction of gravity of the upper body of the robot, the absolute angle of the detected upper body and / or
Based on the absolute angular velocity, the gravity
Estimation of estimating the absolute angle and / or absolute angular rate with respect to direction
Constant means, the absolute angle of the estimated ground site and / or
A target position for changing the target position based on an absolute angular velocity
Changing means, and changing the target position according to the changed target position.
Since it is configured to include a drive control value calculating means for calculating a drive control value of the joint, it is possible to quickly recover to the expected posture even if the robot tilts due to encountering unexpected inclination or unevenness, It is possible to walk stably and improve torpedo in a moving environment.

In the apparatus according to the second aspect, since the predetermined portion is located at the position of the center of gravity, the stability of the posture can be recovered more accurately by setting the position that is the core of the posture control as the control amount. can do.

[0029] In the apparatus according to the third aspect, the detection is performed.
Based on the obtained absolute angle and / or absolute angular velocity of the upper body, the drive control value of the joint closest to the ground contact portion is configured to be corrected together. Therefore, while simplifying the calculation, the displacement speed of the predetermined portion, For example, the control amount is substantially equivalent to the control amount together with the center-of-gravity velocity, and the posture stability can be more smoothly restored.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the entire walking control device of a legged mobile robot according to the present invention.

FIG. 2 is a block diagram showing details of a control unit in FIG. 1;

FIG. 3 is a block diagram illustrating an operation of the control unit in FIG. 2;

[Explanation of symbols]

Reference Signs List 1 legged mobile robot (bipedal walking robot) 2 leg link 10R, 10L leg rotation joint 12R, 12L crotch roll direction joint 14R, 14L crotch pitch direction joint 16R, 16L knee joint Joints in the pitch direction 18R, 18L Joints in the pitch direction of the ankle 20R, 20L Joints in the roll direction of the ankle 22R, 22L Foot 24 Housing 26 Control unit 40 Tilt sensor

Claims (3)

(57) [Claims] 1. A walking control device for a legged mobile robot having an upper body and a plurality of legs , wherein
The predetermined part matches the target position of the predetermined part of the robot.
For driving and controlling the joints of the robot such that: a. Absolute angle and / or the detection means that issues detects the absolute angular velocity with respect to the direction of gravity of the upper body of the robot, b. Absolute angle and / or absolute angular velocity of the detected upper body
Based on time, against the direction of gravity of the ground portion of the robot
Estimating means for estimating an absolute angle and / or an absolute angular velocity , c. Absolute angle and / or the absolute of the estimated ground site
Based on the angular velocity, the target position changing <br/> means for changing the targets position, and, d. Drive control of the joint according to the changed target position
A walking control device for a legged mobile robot , comprising: drive control value calculation means for calculating a control value . 2. The walking control device for a legged mobile robot according to claim 1, wherein the predetermined portion is a position of a center of gravity. 3. The detected absolute angle of the upper body and / or
And correcting the drive control value of the joint closest to the ground contact portion based on the absolute angular velocity.
Item 3. The walking control device for a legged mobile robot according to item 2.