JP3167407B2 - 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 control system for a legged mobile robot, and more particularly, to a bipedal legged mobile robot capable of walking stably even on a road surface having unexpected irregularities.

[0002]

2. Description of the Related Art A technique for calculating a gait in real time has been proposed as a technique for stably walking a legged mobile robot (Legged Robots on Rough Terrain; Experime).
nts inAdjusting Step Length, by Jessica Hodgins. I
EEE, 1988). However, this method requires an enormous amount of calculation, and at present, it is difficult to control such a multi-degree-of-freedom robot with a small and lightweight computer that can be mounted on a mobile robot. On the other hand, as a method to realize walking of a legged mobile robot, gaits are calculated in advance and stored in the memory of a computer mounted on the robot, and walking is performed by performing only simple data processing when walking. For example, a technique described in Japanese Patent Application Laid-Open No. 62-97006 can be cited.

[0003]

According to the latter technique, it is possible to control a multi-degree-of-freedom robot with a small and lightweight computer which can be mounted on a mobile robot.
If a condition different from the previously planned gait condition is encountered, it is not always possible to respond satisfactorily. In addition, it is extremely difficult to calculate a gait on an uneven road surface in advance.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to control a walking of a legged mobile robot using a mountable small and lightweight computer based on a previously designed gait, and encounter an unexpected uneven road surface. An object of the present invention is to provide a walking control device for a legged mobile robot that can stably walk even when the user walks.

[0005]

Means for Solving the Problems In order to solve the above problems, the present invention is configured as follows. Signs described below
With description of those, in the one of claims, the substrate (cylinder
Body) 24 and a plurality of leg links 2 connected thereto
Consists of a said plurality of a walk controller of a legged mobile robot 1 to walk while supporting its own weight alternately leg link, a respective articulation which is set in advance (the hip joints 10R (L)
Outputs the target angle of the etc.) (target joint angle qc) to servomotor placed in each joint at predetermined time DT, the respective Seki
The actual angle of the section (the actual joint angle qf) is to follow the target angle
In controls to so that the detection means (control unit 26 for detecting the posture of the robot, the inclination sensor 4
0, 42, etc. in S18), and the detected posture
Determine whether the robot is in a predetermined posture based on
Attitude determination means (control unit 26, S24, S2
8) wherein the robot deviates from a predetermined posture.
If it is determined , change the predetermined time (control unit
(26, S26, S30, S34) .
Further, in the present invention, the detecting means includes the base.
The body inclination angle θx, θy and / or the inclination angular velocity
Measurement at an absolute angle with respect to the
Predetermined values θx-max, θy-max, second predetermined values θx-min, θ
y-min) to detect the posture of the robot
Configured. Further, according to claim 3, the predetermined value
Can keep the robot stationary or walking
The angle value and / or the angular velocity value should be within the allowable range.
Done. Further, according to claim 4, the base body (body portion)
24 and its first joint (eg, hip joint 10R (L))
And at least a second joint (knee joint 16
R (L), etc.)
The weight is alternately changed by the plurality of leg links.
Control device for legged mobile robot 1 that walks while supporting
Each joint (a hip joint 10R) set in advance.
(L) etc. at a predetermined angle (target joint angle qc)
Output to servo motors arranged at each joint at every DT,
The actual angle (actual joint angle qf) of each joint is the target angle
Wherein the robot is controlled to follow
Detection means (control unit 26, tilt cell
S18), and the detected
Whether the robot is in a predetermined posture based on the posture
Attitude determination means (control unit 26, S24,
S28), wherein the robot deviates from a predetermined posture.
If it is determined that the predetermined time has been
Together with the units 26, S26, S30, S34)
Correct at least one control value for each joint (control unit
, S20, S106, S108, S200 to S22
0).

[0006]

When the legged mobile robot leans forward, for example, when it encounters an unexpected uneven road surface, it is possible to recover its posture by landing earlier than the scheduled time. Further, since the target angle is set in advance, the amount of calculation during walking control is small, and this control can be realized using a small and lightweight computer that can be mounted on a legged mobile robot.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below by taking a bipedal walking robot as an example of a legged mobile robot. FIG.
FIG. 1 is an explanatory skeleton diagram showing the robot 1 as a whole, and includes six joints (axes) in each of left and right leg links 2 (for convenience of understanding, each joint (axis) is electrically driven to drive it). Motors). The six joints (shafts) are, in order from the top, joints (shafts) 10R and 10L for hip rotation.
(R is the right side, L is the left side; the same applies hereinafter), joints (axis) 12R, 12L in the waist pitch direction (x direction), joints (axis) 14R, 14L in the same roll direction (y direction), knee The joints (axes) 16R, 16L in the pitch direction of the joints, the joints (axes) 18R, 18L in the pitch direction of the ankles, and the joints (axes) 20R, 20L in the roll direction, have a foot (foot) below. ) 22R and 22L are attached, and a body (base) 24 is provided at the uppermost position, and a control unit 26 is housed inside. In the above description, the hip joint is composed of joints (axis) 10R (L), 12R (L), 14R (L), and the ankle joint is joints (axis) 18R (L), 2R.
0R (L). The thigh links 28R and 28L are connected between the waist joint and the knee joint, and the crus links 30R and 30L are connected between the knee joint and the ankle joint.

Here, the leg link 2 is provided with six degrees of freedom for each of the left and right feet,
× 2 = 12 joints (axes) can be driven at appropriate angles to give desired movement to the entire foot,
It is configured so that it can walk in a three-dimensional space arbitrarily. As described above, the above-mentioned joint is formed of an electric motor, and further includes a speed reducer that boosts the output thereof,
For details, refer to the application proposed by the present applicant (Japanese Patent Application No.
No. 24218, Japanese Patent Laid-Open No. 3-184772) and the like are not the subject of the present invention, and therefore, further description is omitted.

Here, in the robot 1 shown in FIG.
A known six-axis force sensor 36 is provided at the ankle, and a force component F in the x, y, and z directions transmitted to the robot via the foot.
x, Fy, Fz and moment components Mx,
My and Mz are measured, and the presence or absence of landing on the foot and the magnitude and direction of the force applied to the support leg are detected. A well-known capacitance-type ground switch 38 is provided at each of the four corners of the foot.
Detects the presence or absence of grounding. Furthermore, on the upper part of the body part 24,
A pair of inclination sensors 40 and 42 are provided to detect the inclination with respect to the z-axis in the xz plane and its angular velocity, as well as the inclination with respect to the z-axis in the yz plane and its angular velocity. The electric motor of each joint is provided with a rotary encoder for detecting the amount of rotation (only the electric motor for an ankle joint is shown in FIG. 1). The outputs of the sensors 36 and the like are sent to the control unit 26 in the body 24 described above.

FIG. 2 is a block diagram showing the details of the control unit 26, which comprises a microcomputer. The output of the inclination sensors 40 and 42 is A
The digital value is converted by the / D converter 50, and the output is sent to the RAM 54 via the bus 52. The outputs of the encoders arranged adjacent to the electric motors are input to the RAM 54 via the reversible counter 56, and the output of the ground switch 38 is similarly output to the R via the waveform shaping circuit 62.
Stored in the AM 54. An arithmetic unit 64 is provided in the control unit. The arithmetic unit 64 reads a walking pattern stored in the ROM 66 and calculates a speed command value of the electric motor from a deviation from an actual measurement value sent from the reversible counter 56. The signal is sent to the servo amplifier via the A converter 68. As shown in the figure, the encoder output is sent to the servo amplifier via the F / V conversion circuit, and the speed feedback control as a minor loop is realized as described later.

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

FIG. 3 is a block diagram showing the operation of the control device of FIG. A walking pattern premised on a flat road is designed in advance at an absolute angle (an angle with respect to the direction of gravity) off-line, and coordinate transformation is performed and stored as an angle of a torso and an angle of a joint. The angle, the target joint angle qc (relative angle), and the target joint angular velocity dqc (relative angular velocity) are time-series for 12 joints, specifically, DTsec. Output every (constant value). Here, the target joint angular velocity dqc is equal to the time t sec. Between the target joint angle qc (t) at time tc and the target joint angle qc (t + Δt) at the next time t + Δt (that is, dqc = qc (t + Δ
t) -qc (t)). In order to follow such a target value, as shown in the drawing, a position feedback control and a speed feedforward control are performed to form a joint angle servo system. What is characteristic of the present invention is that the inclination angle θy of the body (base) 24 of the robot 1 described above.
(Absolute angle with respect to the direction of gravity about the y-axis as shown in the lower part of FIG. 1), and the time t is changed when the robot is in an unstable posture. As a result, when the walking pattern encounters an unexpected uneven road surface,
You can walk stably. Hereinafter, the details of this control will be described with reference to the flowchart of FIG.

In the flow chart of FIG.
Initialize parameters and the like by initializing each part of the device in step S12.
To wait for the timer interrupt. This timer interrupt is performed every 5 ms (DTsec. Described above). Subsequently, the process proceeds to S16, where the target value (the time t
sec. , The target angles qc (t) of the twelve joints and a control gain described later) are read, and then S18
To read the output of each sensor and switch to detect the state of the robot.

Then, the program proceeds to S20, in which an operation amount Vout is calculated. Figure 5 subroutine flow showing the work
Describing according to the chart, first, in S100, the basic control amount Vc by the joint angle servo system is calculated as follows: Vc = kp · (qc−qf) + kf · dqc. Here, the basic control value Vc is 1 at each time.
Each of the two joints is calculated in the form of the above-described electric motor speed command value. In the above, qf: actual joint angle, kp, kf: proportional gain (constant or variable)
It is.

Then, the program proceeds to S102, in which the compliance correction amount ΔVc1 is calculated if the free leg lands (the correction amount ΔVc1 and the correction amount ΔVc1 described below).
Means a minute value for correcting the basic control amount. The correction amount is calculated based on the motor speed command value in the same manner as the basic control amount.) As shown in FIG. 6, a dynamic model is assumed for the foot 22R (L), and the entire foot is suspended by a helical spring having a spring rate kcomp around the ankle joint. It is assumed that a rotational displacement proportional to the magnitude of the moments Mx and My applied to the ankle detected via the force sensor 36 is performed. That is, impedance control is realized by speed resolution control. Specifically, the compliance correction control amount ΔVc1 is calculated by ΔVc1 = kcomp · Mx (My). This correction is performed for the ankle joints 18, 20R (L).
And an ankle joint 18R (L) is related to the moment My and an ankle joint 20R (L) is related to the moment M
x. The proportional gain kcomp is constant or variable.

Then, the program proceeds to S104, in which a correction amount ΔVc2 based on the tilt angle and the tilt angular velocity is calculated for the support leg side. As shown in FIG. 7, during the two-leg support period or the one-leg support period, the tilt angles θx, θx of the trunk 24 are attached to the hip joints 12, 14R (L) and the ankle joints 18, 20R (L) of the supporting legs.
Correction amount ΔVc2 according to θy and inclination angular speeds ωx, ωy
Is calculated as follows: ΔVc2 = kθ · θx (θy) + kω · ωx (ωy) That is, the degree of instability of the posture of the robot is detected in accordance with the inclination of the body 24, and the degree of instability is corrected to recover a stable posture. Where the proportional gains kθ, kω
Is constant or variable.

Then, the program proceeds to S106, in which the same control amount ΔVc3 is calculated for the hip joints 12, 14R (L) on the free leg side. Referring to the subroutine flow chart of FIG. 8 showing the operation, first, in S200, the value of the coefficient ku (t) is searched. This is <br/> as shown in FIG. 9, the data having such characteristics to a coefficient which is set to increase over time in the one-leg supporting period of the left leg or the right leg is the ROM66 Is stored as a look-up table. In S200, a search is made according to the elapsed time t from the start of the one-leg support period. Then S2
The process proceeds from 02 onward, and first, a correction amount (referred to as ΔVc3y) in the front-rear direction (around the y-axis), that is, for the joint 12R (L) is calculated. That is, the inclination angle θy in the front-rear direction (around the y-axis) detected in S202 is compared with a first predetermined value θy-max (a value appropriately set in the positive direction as shown in FIG. 9). If it is determined, the process proceeds to S204, in which a value exceeding the first predetermined value θy-max is multiplied by the aforementioned ku (t) and the proportional gain kr (constant or variable) to obtain a correction value ΔV.
c3y is calculated, and when the detected value is determined to be equal to or less than the first predetermined value in S202, the process proceeds to S206, where it is compared with a second predetermined value θy-min (a value appropriately set in the negative direction). When it is determined that the difference is smaller than the predetermined value, the process proceeds to S208, and similarly, the difference is multiplied by ku (t) and kr, and the correction amount Δ
Vc3y is calculated. That is, as shown in FIG. 9, the range is the inclination angle as the robot walking fluctuates, first about it, the second predetermined value [theta] y-max, set in advance the [theta] y-min, defined from them when the inclination angle exceeds was to correct the control value according to the degree beyond. As a result, specifically, as shown in FIG. 10, when the robot leans forward, the free leg lands on the front side from the position expected in the walking pattern, and when the robot leans backward, it lands on the front side. Accordingly, even when the robot 1 encounters an unexpected uneven road surface and loses its posture, the posture can be recovered immediately. The same applies to the left and right directions, as will be described subsequently. When the player leans leftward, the swing leg is corrected further leftward than the position expected in the walking pattern, and when the player leans rightward, the swing leg is corrected further rightward. In addition, these values θy-ma
x and θy-min are the robots shown in FIG.
An inclination angle in a range in which a stable posture can be held when (still) is selected and appropriately set.

In the flowchart of FIG.
If the result in S206 is negative, the process proceeds to S210, and the correction amount is set to zero. The above is the case of calculating the correction amount in the front-rear direction (around the y-axis), that is, the correction amount of the joint 12R (L). This is the operation in the left-right direction (around the x-axis) of the joint 14R (L). The same applies to S212.
When the inclination angle θx in the left-right direction exceeds the first predetermined value θx-max or is smaller than the second predetermined value θx-min in S220, the correction amount (ΔVc3x) is calculated according to the difference. (Note that the characteristics of θx-max and θx-min
The same as θy-max and θy-min shown in (1) are appropriately set.) As shown in FIG. 9, the coefficient ku (t) is set so as to be held during the two-leg supporting period and to decrease with time in the next one-leg supporting period. As a result, once this free leg correction has been made, it is continued from the two-leg support period to the middle of the one-leg support period.

Returning to the flow chart of FIG.
Proceeding to 108, when the above-described correction amount is calculated to the basic control amount Vc, the resultant is added to perform a composite calculation of the operation amount Vout.

Subsequently, returning to the flow chart of FIG.
After outputting the calculated operation amount Vout by proceeding to S2, S
Proceeding to 24, the detected inclination angle θy is compared again with the above-mentioned first predetermined value θy-max, and if it is determined that the value exceeds the predetermined value, the flow proceeds to S26 to determine the next time t + Δt Δ
The value of t is corrected as shown. When the result in S24 is NO, the program proceeds to S28, where the value is compared with a second predetermined value θy-min,
When it is determined that the value is lower than the above, the process proceeds to S30, and similarly, the correction is made as shown in the drawing.
Proceeding to 32, the value of Δt is set to DT (the constant value described above). Subsequently, the process proceeds to S34 to add the determined Δt to determine the next time, reads the target value at that time in S36, and repeats this process until it is determined in S12 that walking is completed. If it is determined that the walking has ended, the necessary post-processing is performed in S38, and the control ends.

In other words, in this control, basically, each joint is controlled so as to reach a target angle qc (t) at a predetermined time (Δt = DT). When the angle exceeds the predetermined range (θy-max, θy-min), it is determined that the posture is unstable, and the time (update unit Δt) serving as a reference of the target angle to be updated (S26, S30).
The correction was made as shown in FIG. (In S26 and S30, kt1 and kt2 are constant or variable coefficients.
1, kt2> 0). That is, when it is determined that the inclination angle exceeds θy-max, the value of Δt is
Correction was made so as to be larger than T, and data preceding the schedule in time was used as the target angle. As a result, for example, when the robot encounters an uneven road surface and leans forward, the free leg can be landed earlier than the scheduled time, and the collapsed posture can be quickly recovered. Conversely, when the value is smaller than θy-min, the value of Δt becomes smaller than the fixed value DT in the equation of S30, and the data following the schedule in time is set as the target angle. As a result, when the robot leans backward, it lands later than the scheduled time, and the collapsed posture can be quickly recovered in the same manner (in S30, Δt becomes a negative value in an extreme case, In that case, the target angle used once will be used again). still,
In the case where the data corresponding to the time t + Δt is not stored in the above, the data closest in time to that is used or calculated by interpolation.

In this embodiment, as described above, the reference time of the target value is corrected according to the inclination of the body in the control device of the bipedal legged mobile robot having the joint angle servo system. Even when the walking pattern encounters an unexpected uneven road surface, the user can always walk stably. In this control, since the target value is set in advance,
This can be realized using a small and lightweight computer that can be mounted on a legged mobile robot. Furthermore, since the control amount of the support leg and the free leg is also corrected according to the inclination, more stable walking can be expected, and the compliance control is performed at the time of landing, so that the impact at the time of landing can be improved. Can also be well absorbed.

In the above-described embodiment, various corrections for correcting the time and the basic control amount have been described. However, all of these corrections need not be performed and may be arbitrarily selected.

Further, S26 and S26 in the flow chart of FIG.
In S30, θy-max and θy-min used in S202 and S206 of the flow chart of FIG. 8 are used again, but other values may be used.

Although the time is corrected from the inclination angle, the time may be corrected using the inclination angular velocity.

Furthermore, as shown in FIG. 3, the walking pattern is set in advance by an absolute angle, but the present invention is not limited to this. The walking pattern may be set by a relative joint angle. Further, as the walking pattern, not the angle, but high-level conceptual data such as the center of gravity trajectory and the toe trajectory may be set.

Furthermore, although the present invention has been described with reference to a bipedal legged mobile robot, the present invention is not limited to this and is applicable to a legged mobile robot having one or three or more legs.

[0028]

In the claims 1 according to the present invention consists of a substrate and a plurality of leg links coupled thereto, walks while supporting its own weight alternately said plurality of legs link legged a walk controller of the mobile robot, and outputs the servomotor placed in each joint of the target angle of each joint which is set in advance for each predetermined time, the actual angle is the target angle <br/> of each joint in controls to follow the, detection means for detecting a posture of the robot, and the detected posture
It is determined whether the robot is in a predetermined posture based on the
Posture determining means for determining the posture of the robot.
When it is determined that the off-energized, so was to change the predetermined time, it is possible to realize by using a computer small and lightweight enough to be installed in a legged mobile robot, legged mobile robot For example, when the vehicle encounters an unexpected uneven road surface and leans forward, it is possible to land earlier than the scheduled landing time, and thus a stable walking can be always realized.

In the apparatus according to the second aspect, the detection means may measure the inclination angle and / or the inclination angular velocity of the base with an absolute angle with respect to the direction of gravity, and compare the measured value with a predetermined value. The posture of the robot is detected, so when the robot loses its posture, it can be accurately detected. As a result, even when walking on an unexpected uneven road surface, the posture can be more effectively controlled. be able to.

[0030] In the apparatus of claim 3, wherein, since as the predetermined value is an angle value and / or the angular velocity values of the range the robot can hold the stationary state or a walking state, the robot posture It is possible to more accurately detect the possibility of falling due to collapse.

[0031] In the fourth aspect, wherein, coupled through the substrate, it the first joint, its at least a second joint
Respectively made up of a plurality of legs links made have, the <br/> by a plurality of legs link a walk controller of a legged mobile robot which walks while supporting the weight alternately, outputs a preset target angle of each joint was to the servo motor was placed to <br/> in each joint every predetermined time, so that the the actual angle of each joint to follow the eye <br/> target angle in controls, the detection means for detecting a posture of the robot, and the detected
Whether the robot is in a predetermined posture based on the posture
Attitude determination means for determining whether the robot is
When it is determined that deviates from the constant posture, as well as changes the predetermined time, the since so as to correct at least one control value of each joint, the enough to be installed in a legged mobile robot lightweight Even when walking on an unexpected uneven road surface using a computer, the user can always walk in a more stable posture.

[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 an explanatory block diagram of a control unit shown in FIG.

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

FIG. 4 is a main diagram showing the operation of the control unit shown in FIG. 2;
It is a flow chart.

FIG. 5 is a subroutine flowchart showing an operation amount calculation operation in the flowchart of FIG. 4;

FIG. 6 is an explanatory diagram illustrating compliance control performed in the flowchart of FIG. 5;

FIG. 7 is an explanatory diagram showing correction by inclination of a support leg performed in the flow chart of FIG. 5;

FIG. 8 is a subroutine flowchart showing a correction amount calculation based on the inclination of the free leg performed in the flowchart of FIG. 5;

FIG. 9 is a timing chart illustrating control of the flowchart of FIG. 4;

FIG. 10 is an explanatory diagram illustrating inclination correction of a free leg in the flow chart of FIG. 8;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Legged mobile robot (biped walking robot) 2 Leg link 10R, 10L Joint for rotation of waist leg (axis) 12R, 12L Joint of waist pitch direction (axis) 14R, 14L Joint of waist roll direction (Axis) 16R, 16L Joint of pitch direction of knee (axis) 18R, 18L Joint of pitch direction of ankle (axis) 20R, 20L Joint of roll direction of ankle (axis) 22R, 22L Foot (foot) 24) Body 26 Control unit 36 6-axis force sensor 38 Grounding sensor 40, 42 Tilt sensor

Claims (4)

(57) [Claims] 1. A walking control device for a legged mobile robot comprising a base and a plurality of leg links connected thereto, wherein the walking control device walks while supporting its own weight alternately with the plurality of leg links. and outputs to the servo motor that placed in each joint of the target angle of each joint which is set in advance for each predetermined time, the
In a control system in which the actual angle of each joint follows the target angle, a. Detecting means for detecting the posture of the robot ; and b. The robot determines a predetermined position based on the detected posture.
It is provided with a position determining means for determine a constant whether the posture, and said robot is out of the predetermined posture determination
When the determination, walk controller of a legged mobile robot, wherein the benzalkonium change the predetermined time. Wherein said detecting means, that the inclination angle and / or tilt angular velocity of the substrate measured by the absolute angle relative to the direction of gravity, and to detect the posture of the robot measurements is compared with a predetermined value The walking control device for a legged mobile robot according to claim 1, wherein: 3. The legged mobile robot according to claim 2, wherein the predetermined value is an angle value and / or an angular velocity value within a range in which the robot can hold a stationary state or a walking state. Walking control device. 4. A base body and a plurality of leg links connected to the base via a first joint and each having at least a second joint, wherein the plurality of leg links are alternately provided by the plurality of leg links. a walk controller of a legged mobile robot which walks while supporting the weight, and outputs the servomotor placed in each joint of the target angle of each joint which is set in advance for each predetermined time, the fruit of the joints So that the angle follows the target angle
, Wherein: a. Detecting means for detecting the posture of the robot ; and b. The robot determines a predetermined position based on the detected posture.
It is provided with a position determining means for determine a constant whether the posture, and said robot is out of the predetermined posture determination
When the determination, the while changing the predetermined time, the walk controller of a legged mobile robot, wherein the benzalkonium to correct the at least one control value of each joint.