Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1998-02-25
2001-08-14
Wachsman, Hal (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S151000, C702S177000, C100S245000, C100S253000, C100S260000
Reexamination Certificate
active
06275778
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to location-force target path creators, and more particularly to a location-force target path creator adapted to create a smooth form of a time function with a plurality of target values among in location, position, force or moment that are given for a force control system.
Where realizing a force control system for robots or machine tools, the process as shown in
FIG. 11
is usually carried out. That is, at step
1
(hereinafter denoted as S
1
in the figure), the instructions from an operator is interpreted as data as to location, force, position, moment, etc. Then, at step
2
, a working region, a maximum speed, etc. are determined depending upon the data, etc. obtained at step
1
for calculating in what way a robot or the like is operated for its feasibility, thereby planning the path thereof. At step
3
, the coefficient data, etc. for a target value function is calculated to establish a target value function, to thereafter calculate and output target paths in real time. At step
4
and the subsequent steps, feedback control is made based on the calculated target paths. At step
5
, the target path data is applied to a mechanism section, such as a motor and a driver, of which force or torque is to be controlled so that the amount thereof is fed back at step
6
. In the motion control structure as set forth above, the processes of step
1
through step
3
are for planning wherein target values in location and force are created.
However, although conventionally there have been often studies on force control shown in step
4
and the subsequent steps, it is the practical situation that studies were rarely made for the planning section. Meanwhile, as regard to studies on force control, there is often a case that the reference input to a force control system is limited to step inputting or it is handled as ambiguous one without definition. This seems to be a factor that the effectiveness cannot be appreciated to a full extent, even where a robust force control system can be applied to an actual system. On the other hand, where the location and position only are designed for target paths, they are, though effective for actuation such as gripping and releasing in three dimensions, difficult to apply to such a control operation that involves force of assembling, grinding and debarring, etc. If a force reference input is used for step input as above, a kind of impact occurs at non-continuous portions with a fear of causing residual vibrations, deformations, breakage, etc.
The present invention has been made in view of the conventionally-encountered problems, and it is the object of the present invention to provide a location-force target path creator which is capable of creating a smooth form of a time function with a plurality of target values among in location, position, force and moment given to a force control system.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is structured a location-force target path creator for creating a smooth form of a time function from a plurality of target values in location, position, force and moment given for a force control system, the force control system having degrees of control freedom as to a plurality of ones among in location, position, force and moment, comprising: a node setting means for setting, as nodes, the target values together with time for which the target value is applied; a time region dividing means for projecting, as a logical sum in the degrees of control freedom, the nodes set by the node setting means onto a time axis to divide a time region; an element motion designing means for calculating a target path function in the form of a third order or fifth order polynominal while providing a boundary condition to each time region divided by the time region dividing means.
A motion plan with target path creation is tried for a hybrid control system involving location and force. That is, a target path as to force/moment, together with a location/position target path, are designed as a third order or fifth order polynominal so as to realize such arbitrary force/moment that a human acts upon an object in his actual operation. Specifically, determination is first made for a plurality of target values among in location, position, force and moment. The target values, together with time for applying the target value, are set as nodes. The nodes are determined as to degrees of control freedom. These nodes are projected onto a time axis. The projected nodes are represented as a logical sum for the degrees of freedom. As a result, a time region is divided into the number of nodes. The minimum unit of motion in a divided time region is taken as an “element motion”. Then, a target path function is designed for the element motion. The target path function is designed in the form of a third order or fifth order polynominal. If a fifth order polynominal is adopted, it is considered that a function closer to human motion can be realized with higher approximation. The polynominal can be readily solved by providing boundary conditions thereto. A series of motions created by connecting, in order, a plurality of element motions is considered as a “unit motion”. Also, a set of a plurality of unit motions is taken as a “motion”. The target paths thus created is not independent on an element motion basis but constitutes a series of unit motions. Therefore, the acting of force or the like is smoothened to provide motions with higher analogous to human motion. This, in turn, can prevent residual vibrations, deformations or breakage from occurring at nodes.
REFERENCES:
patent: 4773025 (1988-09-01), Penkar et al.
patent: 4774445 (1988-09-01), Penkar
patent: 5544282 (1996-08-01), Chen et al.
patent: 5988850 (1999-11-01), Kumiya
Mita Tsutomu
Shimada Akira
Adams & Wilks
Seiko Instruments Inc.
Wachsman Hal
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