JP3029286B2 - Robot and robot control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a robot in which a work parameter required to execute a work restricted by a work target is accompanied by the robot itself. And a robot control method.

(Conventional Method) When a robot performs a task, it is generally necessary to teach the robot in advance work parameters such as a work procedure and a relative positional relationship between the robot and a work object. When the operation to be performed is to bind the robot, it is necessary to teach not only the relative positional relationship between the robot and the work target but also the binding direction in advance. Even if the teaching is performed in this manner, for example, in the case of a work in which the robot is bound, an error often occurs in the relative position between the robot and the work target. Such an error is
In general, the hand of the robot is made flexible by mechanical or control so as to absorb it.

However, in such a conventional control method, when work parameters such as a relative distance between the robot and the work object and a binding direction received by the robot are not known in advance,
Even if the robot's hands have flexibility, they cannot work. For this reason, there has been a problem that the use range of the robot is limited to a narrow range such as a production site.

(Problems to be Solved by the Invention) As described above, in the conventional method of controlling a robot, unless a work parameter such as a relative position between the work target and the robot or a binding direction received by the robot is known in advance, the robot is operated by the robot. Therefore, there is a problem that the working range in which the robot can be used is limited because the robot cannot be operated.

Therefore, the present invention can automatically perform the work even when the work parameters such as the relative position between the work object and the robot and the binding direction received by the robot from the work object are not known in advance. Accordingly, it is an object of the present invention to provide a robot and a control method of the robot which can contribute to expansion of a use range of the robot.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, in the robot and the robot control method according to the present invention, the robot is controlled by controlling the force applied to the external environment by the hand of the robot. Give the hand virtual stiffness to give the hand flexibility, hold the work object with the hand part of the hand in this state, and then groping with the hand bound by the work object, At this time, by analyzing the information obtained by measuring the position of the hand of the robot and the force applied to the hand based on the knowledge about the work procedure given as internal information in advance, the relative position of the work object and the robot is Work parameters such as a distance and a binding direction given to the robot by the work object are identified. The small errors remaining after identification are absorbed by the flexibility of the robot's hands.

(Operation) In the above control method, since it is not necessary to give in advance the work parameters such as the relative distance between the work object and the robot and the direction in which the robot receives the constraint from the work object, the above work parameters are not known in advance. Even
It becomes possible for the robot to automatically perform the work.

(Embodiment) Hereinafter, an embodiment of a control method of the present invention will be described with reference to the drawings.

FIG. 1 shows a robot 11 to which the control method of the present invention is applied to execute a task of rotating a crank 1 in a direction indicated by a solid arrow 2 in the figure.

The robot 11 can be roughly divided into an arm 12 having a plurality of joints, a hand 13 attached to the tip of the arm 12, and a force sensor 14 attached to the hand 13.
And a control device 15 for introducing the output of the force sensor 14 and the output of the position sensor provided at each joint to control the arm 12, the hand 13, and the hand of the hand 13.

The control device 15 stores knowledge information about a work procedure to be described later, the knowledge information, the output of the force sensor 14, and the output of the position sensor provided at each joint.
An algorithm for calculating how to move 12 and a control system for controlling hand 13 and arm 12 based on the calculated result are provided.

Specifically, work is performed according to the flow shown in FIG. In this example, the crank 1 is rotated by the robot 11.

First, in the control device 15, as knowledge about the work procedure of the crank rotation, `` the hand part of the hand of the robot grasps the handle of the crank, and follows a circular orbit having a certain radius constrained on a certain plane. It must be moved while being constrained in the radial direction. " The work parameters that must be obtained at this time are the constraint plane coordinates, the center coordinates of the circular orbit, and the radius of the circular orbit.

First, when started, knowledge about the above-described work procedure, in this case, knowledge about the cranking work procedure is read (step f ₁ ).

Next, the hand 13 is given flexibility by controlling the force applied by the hand 13 to the external environment so that the hand 13 of the robot 11 behaves as if it has virtual stiffness expressed by the following equation (step f _2).

F = then _{K (x d -x h) ...} (1), to grip the handle of the crank 1 by touch with hand portion of the end 13 with the rigidity of such a virtual (Step f _3). At this time, even if the position of the handle of the crank 1 is uncertain, if a part of the handle is in a space that can be gripped by the hand of the hand 13, the virtual rigidity of the hand 13 shown in Expression (1) indicates The robot 11 can hold the handle.

Next, with the current position of the hand 13 as a starting point, linear target trajectories x _{d (i)} are sequentially formed in parallel with the three axis directions of the reference coordinate system, and the target trajectory is set to the target trajectory while holding the handle of the crank 1. Therefore, the hand 13 is moved. At this time, if the handle is successfully grasped, the hand 13 moves following the restraint of the crank 1 due to its flexibility. However, when error occurs between the trajectory x _h of the target trajectory x _d and the hand 13, (1) hand 13 exerts a force to the crank 1 according to Formula wrist its reaction force of the robot 11 It is measured by a force sensor 14 provided in the section.

This by force sensor 14 force is detected, moreover regarded as an error between the trajectory x _h of the target trajectory x _d and the hand 13 is in when generated, the hand portion of the hand 13 has successfully gripped the crank 1 the handle . Conversely, the hand 13 without being constrained by the crank 1, when moving to the street to both target trajectory x _d of the three directions, regarded as the hand unit has failed to grip the handle (step f _5). If you fail to grip the handle,
Performing a gripping operation of the handle again returns to step f _3.

If the hand portion of the hand 13 has successfully gripped the crank 1 the handle, the trajectory x _h of the hand 13 becomes trajectory following the binding of the crank 1. Therefore, sampling the information track x _h of the hand 13 at appropriate intervals (Step f _6), to identify the rotational radius and the rotational center of the crank 1, and generates a trajectory of the crank turning using these information ( Steps
f ₇ ).

This trajectory is generated as follows. That is, considering the geometrical condition satisfying the trajectory bound to the crank 1 in consideration of the above-mentioned knowledge on the work procedure and the work parameter to be obtained, when x is a point on the trajectory, ) Point x is on a certain constraint plane. (Ii) Point x is on a circular orbit.

Therefore, the sampling data x _{h (i)} (i = 1, 2, 3,...)
n) is assumed to be a point on the trajectory following the constraint of crank 1, and a vector group v _(i) = xh _(i) -xh _(i) (i ≠ j) represented by the following equation: When (2) is obtained, from the condition (i), v _(i) is a vector group parallel to this constraint plane.

Next, a common unit normal vector b perpendicular to v _(i) is obtained using the least squares method. Further, unit vectors n and t perpendicular to the vector n are obtained. Using n, t, b as basic vectors, a new coordinate system O'-xyz whose origin position is the same as the origin position of the reference coordinate system O-xyz is introduced. Here, assuming that R = [n, t, b] (3) is used as the rotation matrix R, the sampling data expressed in the reference coordinate system
x _{h (i)} (i = 1,2,3,... n) is converted to a point x ′ _{h (i)} (i = 1,2,3,. Is converted.

_{x'h (i)} = ^RT * _{xh (i)} (4) At this time, as is clear from the derivation method, the point _{x'h (i)} is parallel to the z-plane in the coordinate system O'-xyz. Points on the circumference on a simple plane. That is, x ′ _{h (i)} satisfies the following equation.

(X _i −x ₀ ) ² + (y _i −y ₀ ) ² = r ² z _i = z ₀ (5) where x ′ _{h (i)} = (x _i , y _i , z _i ) ^T , x ₀ = (x ₀ , y ₀ ,
z ₀ ) ^T , x ₀ is the coordinate of the center of the crank in the coordinate system O′-xyz, and r is the turning radius of the crank. Here using the least squares method, first determine the x _0, y _0, then determine the r, determine the z ₀ from the average value of the last z _i.

For example, in the robot 11 in which the hand 13 has the rigidity represented by the expression (1), the trajectory _{x'c (i)} = ( _xci , _yci , _zci ) for rotating the crank represented by the following expression. ^T is determined using x ₀ and r.

x _ci = r · cos (ω _(i) ) + θ ₀ ) y _ci = r · sin (ω _(i) + θ ₀ ) (6) z _ci = z ₀ This x ′ _{c (i)} is transformed into the following coordinate. x _{c (i)} = R · x ′ _{c (i)} (7) If it is obtained as the crank rotation trajectory x _{c (i)} in the reference coordinate system O-xyz, x _{c (i )}
, The crank 1 can be turned. In this case, the radial direction of the crank 1, the direction perpendicular to the binding plane,
Regarding the restriction in the direction of prying the handle, the flexibility of the hand 13 is absorbed, and the follow-up of the hand 13 to xc _(i) is caused by a force generated according to the equation (1) with respect to the generated error. This is done by moving the hand 13 to correct.

Note that ω _(i) is a function that determines the rotation speed of the crank 1, and θ ₀ is a parameter that determines the starting point of the trajectory. These are determined from a work strategy perspective. For example, currently, the handle portion of the hand 13 has gripped the handle of the crank 1, in the case where the starting point of the position x _s crank turning of the hand portion of this time, by determining the theta ₀ as follows I just need.

First, a point x ' _s x' _s = R ^T x _s ... (8) in which the point x _s is represented by the coordinate system O'-xyz is obtained by equation (4). Next, a point NEW x ′ _s is obtained by the following equation.

NEW x ′ _s = x ₀ + r / | x ′ _s −x ₀ | (9) Since NEW x ′ _s is a point on the circumference given by Expression (6), NEW x ′ _s is the starting point. Then, assuming that ω _(i) = 0,
From equation (6), if NEW x ′ _s = (x _s , y _s , z _s ) ^T , x _s = r · cos (θ ₀ ) y _s = r · sin (θ ₀ ) (10) z _{From s} = z ₀ , θ ₀ is obtained by the following equation.

θ ₀ = tan ⁻¹ (y _s / x _s ) (11) Thus, the constraint plane, the radius of the constraint circular orbit, and
Will be operating parameters consisting of the center point coordinates have been determined, the robot 11 based on the operating parameters performs crank turning (step f _8).

In the present invention, the control target is not limited to the crank rotation, and it goes without saying that various operations similar to this can be performed.

[Effects of the Invention] As described above, according to the present invention, even if knowledge about a work procedure is known, work parameters are uncertain and work is subject to constraints, the robot itself can use it. Work parameters can be identified, which allows the robot to perform work automatically.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a robot to which the control method of the present invention is applied, and FIG. 2 is a flow chart for explaining the control method of the present invention. 1 ... crank, 11 ... robot, 12 ... arm, 13 ...
... hand, 15 ... control device.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G05B 19/4155 B25J 9/10

Claims (3)

(57) [Claims] An arm having a joint, a hand attached to a tip of the arm, a force sensor attached to the hand, a position sensor provided at the joint, and an output of the position sensor And a control device for controlling the arm and the hand in accordance with a designated work procedure.The control device acquires knowledge about the designated work procedure from knowledge about work procedures stored in advance. A first means for reading, and a second means for controlling the arm in a state where the hand has flexibility by controlling a force applied to the external environment by the hand and allowing the hand to face the work object. Means and control to move the hand along the target trajectory, at this time, sampling and measuring information on the actual trajectory to which the hand moves, using these information Third means for calculating a work parameter required to execute the work described in the knowledge about the specified work procedure, and performing the work according to the specified work procedure using the calculated work parameter. A robot comprising: the arm and fourth means for controlling the hand to be executed. 2. A robot according to claim 1, further comprising: an arm having a joint, a hand attached to a tip of the arm, a force sensor attached to the hand, and a position sensor provided at the joint. A first step of reading knowledge about the specified work procedure from knowledge about the work procedure stored in advance in causing the hand to perform work in accordance with the specified work procedure; A second step of controlling the arm in a state in which the hand has flexibility by controlling the force applied to the environment so that the hand faces the work object, and moving the hand along a target trajectory. At this time, information about the actual trajectory where the hand moves is sampled and measured, and the knowledge about the designated work procedure is recorded using the information. A third step of calculating a work parameter necessary to execute the specified work, and controlling the arm and the hand to execute the work in accordance with the specified work procedure using the calculated work parameter And a fourth step of controlling the robot. 3. In the second step, when the hand moves along a target trajectory, it is determined that the hand is not restrained by the work object, and the hand is again operated by the work. The method of controlling a robot according to claim 2, wherein an operation of causing the robot to face an object is performed.