positional errors in robot?

Answer 1

There are 2 possibilities in which errors can occur. The Motion control system or the mechanical system.

Think of the robot's drive systems as separate axes.

The drive motor on an axis is usually monitored by an Encoder or Resolver which is fed back to the computer so that it knows how far and how fast the axis is moving. These pulses can sometimes skip due to interferance which can cause an inaccurate reading by the controller. Therefore the computer thinks it's in the correct position but the motor isn't in the correct position. Each Encoder is usually equipped with a check pulse at every revolution (or 1000pulses for linear systems) to ensure that these accuracies do not occur but some controllers do not use this check pulse to verify position.

Further, if any part of the drive system is worn, dirty, loose, friction driven, flexible, bent, etc, there is a possibility that the controller has moved the motor the correct number of revolutions but the position is incorrect.

Answer 2

Yes they occur.

Depending on the configuration of the robot, linear motion is achieved by the coordination of multiple rotary and linear axes (or sometimes - all rotary axes). If the robot is being commanded to move in a linear motion path that required involvement of all 6 axes, then any given error on any one of the axes will result in a cumulative error along this straight path.

If you are doing operations that are sensitive to linear motion (drilling a hole, for example), use an end-of-arm tool to give you about 6 inches of linear travel normal to the tool faceplate of the robot. That way, the end-of-arm tool may be positioned, but the EOA tool actually performs the drill movement using its one and only axis of motion (linear normal to the faceplate), rather than relying on the six individual axes of the robot to coordinate and create the motion.

Answer 3

1. check the position mechanism for mechanical failure.
2.after ensuring that mechanically it is ok,check the recommended signal levels of position controller.
3. if position controller is ok,check further feed back signal for the position controller.
4. also check psition error command signal.
5. before proceeding all above steps ensure that all the sensors are clean and working.

Answer 4

the design team should create the joints to move in a manner that it specific to its function.