1990-09-01

Development of a Real Time Sensor Feedback Robot 901706

In today's manufacturing environment, it has become necessary to develop intelligent robots which are adaptable to changing process requirements. To attain this goal, a key robot technology involving new real time control algorithms has been developed. The algorithms govern the 3D position and orientation of the robot.
Initially, a simulation method was used to study the achievable system accuracy. From the results of computer simulations, it was determined that the algorithms can achieve a high tracking accuracy of ± 0.5 mm at a velocity of 300 mm/sec (4 times higher than conventional sensory control speeds).
For a sensory feedback system, delays in tracking movements are inherent. This is due to the calculation time required for control and to the servo response. To solve this problem, a sensor is positioned at a predetermined distance in advance of the tool in the direction of travel. Sensor data and the same timing data of actual robot arm positions are then used to derive a partial tracking model of workpiece as a target path.
With this developed system, much benefit can be obtained as follows:
  1. 1)
    Applicable to tracking many kinds of tracing to the work profiles. (e.g., seam and edge tracking,constant relative orientation, or constant force).
  2. 2)
    3D position and orientation compensation.
  3. 3)
    Continuously adaptable for various robot speeds.
  4. 4)
    Requires the addition of only one control board for a standard robot controller.
Actual results of this real time sensor feedback system have achieved the same accuracy predicted by the simulation. Thus, the system can achieve maintained process quality and gain productivity in manufacturing.
Robot automation is steadily progressing, with most robots utilizing the teaching playback method of path programming. Presently, this approach requires accurate fixture and jig setting to ensure manufacturing quality, as well as path program modification. To overcome these difficulties, sensor feedback robots with various control techniques have been studied. The authors have developed a sensor feedback robot capable of high precision workpath compensation using information obtained via a flange mounted sensor.
The outline and evaluation result of the development are reported in this paper.

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