Electricity: motive power systems – Positional servo systems – Adaptive or optimizing systems including 'bang-bang' servos
Reexamination Certificate
2001-10-27
2004-02-24
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Positional servo systems
Adaptive or optimizing systems including 'bang-bang' servos
C318S568220, C318S621000, C318S632000
Reexamination Certificate
active
06696809
ABSTRACT:
TECHNICAL FIELD
The present invention relates to robots, servo circuits, actuators, robot control methods, and actuator driving methods, and can be applied to, for example, two- or four-legged mobile robots. The present invention allows the moment of inertia of a driver and the like to be detected in real-time without providing special sensors, by controlling an actuator based on a control object, a result of detecting the movement of the actuator and a response from a standard mathematical model of the actuator; and also in a servo system or the like, by correcting a control value so that responses from an object to be driven and a model of the object to be driven are identical and moreover, by detecting at least the moment of inertia of the object to be driven based on a result of the control value correction.
BACKGROUND ART
Hitherto, a legged mobile robot that uses two legs to move can be moved with the two legs by controlling a plurality of joint actuators provided in the legs.
FIG. 8
is a skeleton view showing a schematic construction of a two-legged mobile robot of the above-described type. A right leg
3
R and a left leg
3
L are joined to a body
2
.
For the right leg
3
R and the left leg
3
L, actuators for controlling joint angles are provided corresponding to, for example, thighs, knees, and ankles, and the right leg
3
R and the left leg
3
L are joined to the body
2
by actuators M
1
R and M
1
L that rotate treating the vertical direction as a rotational axis. Here, for the joints corresponding to the thighs and the ankles, actuators M
2
R and M
3
R, and M
2
L and M
3
L that rotate regions lower than the thighs back and forth and right and left are provided, and for the joints corresponding to the knees, actuators M
4
R and M
4
L that rotate regions lower than the knees back and forth are provided. In addition, for the joints corresponding to the ankles, actuators M
5
R and M
6
R, and M
5
L and M
6
L that rotate regions which are in contact with the ground back and forth and right and left are provided.
A legged mobile robot
1
detects the operations of the actuators M
1
R to M
6
R and M
1
L to M
6
L using sensors, and uses a servo loop to control the operations of the actuators M
1
R to M
6
R and M
1
L to M
6
L. In the body
2
of the legged mobile robot
1
, an attitude sensor (gravity sensor for detecting the direction of gravity) that detects an attitude is provided, and a force sensor, a contact sensor, etc., are provided in each region of the legs
3
R and
3
L, whereby these sensors detect an inclination or the like of the body
2
and correct a control object in each servo loop. These enable this type of robot to perform two-leg walking by setting the control object in each servo loop so that the attitude is successively changed.
FIG. 9
is a block diagram showing a servo circuit that drives an actuator and a control system positioned higher than it. In the legged mobile robot
1
, a control command generator
11
executes, for example, interpolation-operation processing using a basic control object for each actuator, which is used for two-leg walking, whereby a control object value for each actuator is sequentially generated. The control command generator
11
sequentially outputs each control object value to the servo circuit
12
, and inputs each control object to an optimization regulator
13
. In
FIG. 9
, the reference letter S is a Laplace operator.
Each servo circuit
12
uses a multiplier
15
to multiply a differential value of each control object value by gain coefficient Kf. Also, each servo circuit
12
acquires the rotational speed information Vm of each actuator and displacement information Pm based on a rotation angle by using an output from the sensor provided for each actuator. Disturbance Td, caused by, for example, roughness of a floor, is added to the rotational speed information Vm and the displacement information Pm.
Each servo circuit
12
generates an error signal “ep” by using a subtractor
14
to subtract the displacement information Pm from the control object value, and uses a multiplier
16
to amplify the error signal ep by gain coefficient Kp0. Each servo circuit
12
adds thus obtained outputs from the multipliers
15
and
16
, and outputs the sum to an actuator driving circuit
18
.
A subtractor
20
, which is provided for each control object value, subtracts each control object from the corresponding displacement information Pm, and inputs the obtained value to the optimization regulator
13
.
The optimization regulator
13
acquires the displacement information Pm from each servo circuit, and acquires a detection result from each sensor such as an attitude sensor. Thereby, when a control object value, caused by two-leg walking, is output from, for example, the control command generator
11
to each servo circuit, the optimization regulator
13
monitors the state of each actuator operated by each servo circuit, and monitors a change in the attitude, contact with the ground, etc., thereby outputting, based on the monitoring results, the amount of operation for correcting performance of each servo circuit so as to cope with roughness of the ground.
The driving circuit
18
controls the rotation of the motor M by so-called “PI control”. In other words, the driving circuit
18
adds the amount of operation to an output value eV generated based on the error signal ep by an arithmetic circuit
24
, and subtracts the rotational speed information Vm of a motor main unit
22
as the driver. The driving circuit
18
computes a torque Tm which is required for driving the motor M by using a multiplier
25
and an integrator
26
to sequentially process the arithmetic processing result, and the motor M is driven by current driving in accordance with the torque Tm.
Accordingly, the motor M has such a small coefficient of static friction as can almost be ignored. Thus, the use of moment of inertia Jx and coefficient of viscous friction Dm can express a transfer function as a motional impedance. Therefore, in
FIG. 9
, the motor M, each integrator, each multiplier, etc., are indicated using the representation in Laplace operation. The motor M outputs the displacement information Pm by using a position-detecting sensor
19
provided on the rotational axis.
This enables the legged mobile robot
1
to correct the control object in each servo circuit based on a detection result obtained by the attitude sensor, etc., whereby, when the legged mobile robot
1
walks on a rough floor thereon, it changes the positions of joints of the ankle, the center of gravity, etc., in accordance with the roughness on the floor.
In the case that a control object in each servo circuit is corrected based on a detection result obtained by an attitude sensor, etc., as described above, a force sensor, a contact sensor, etc., must be provided for each component constituting legs, and the provision for each component causes a problem in that the entire structure is complicated and enlarged.
The enlargement and increase in weight causes a further problem in that increasing the operation speed of the entire robot is difficult. A force sensor for this type has small rigidity, which makes it difficult to accelerate the operation speed of the entire robot.
Moreover, when it becomes difficult to cope with an unpredictable change in a load, the movement is unstable due to the load change depending on the level of difficulty. Therefore, after all, with contact sensors provided for parts that touch the ground, it is required that the load change be predicted.
In the above-described construction in
FIG. 8
, concerning the motors M
6
R and M
6
L for rotating the ground-contact parts the right and left, at the moment the left foot breaks contact with the floor after the right foot touches the floor, the load moment of inertia of the motor M
6
R for the right foot is maximum, and the load moment of inertia of the motor M
6
L for the left foot is minimum. In walking, the load moment of inertia repeatedly reaches its maximum and minimum, and the attitude of the entirety ca
Ishii Shinji
Kuroki Yoshihiro
Frommer William S.
Frommer & Lawrence & Haug LLP
Kessler Gordon
Ro Bentsu
Sony Corporation
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