Rotary shaft encoders are devices which are employed to indicate the motion of parts of machinery. In particular, rotary shaft encoders are widely employed to measure the motion of the joints in robotic machinery. With the rise in the employment of robotics in manufacturing, such rotary shaft encoders have become very widely employed.
There is a problem related to the extensive use of such rotary shaft encoders when there is some failure in the operation of the robot or other controlled machine which employs such rotary shaft encoders. In many instances the shaft encoder is suspected in the failure. Currently, there is no reliable and proven method for testing such rotary shaft encoders to determine whether the machine failure is due to a failure in the shaft encoder. There are two primary solutions attempted to this problem, each having significant drawbacks.
In a first attempt to solve this problem service involves testing the rotary shaft encoder in place. An oscilloscope probe or the input probe of some other monitoring device is attached to the output lines of the rotary shaft encoder while the rotary shaft encoder is in place within the controlled machine. Then the joint is moved, either by hand or via a controlled movement by the machine itself. This technique is not satisfactory for several reasons. Firstly, it is difficult and sometimes dangerous to attach the oscilloscope probes to the rotary shaft encoder outputs while in place in the machine. In addition, attempting to move the machine to generate the shaft encoder outputs for testing may be difficult or impossible, particularly in light of the fact that the controlled machine is out of order in some manner. Lastly, it is possible that the fault is not in the shaft encoder but rather in the machine itself. For example, if the rotary shaft encoder is not supplied with the proper working voltages or if the outputs are improperly loaded, the output of the rotary shaft encoder will appear incorrect even though the fault is in other parts of the machine and not in the rotary shaft encoder.
The second manner of testing of such rotary shaft encoders in the prior art requires removal of the rotary shaft encoder from the controlled machine. In this case, the rotary shaft encoder is set up on a laboratory bench and supplied with proper working voltages. As in the previous case, the outputs of the rotary shaft encoder are applied to an oscilloscope or other monitoring apparatus to determine whether or not they are proper. In most cases the operator attempts to simulate the operation of the machine by spinning the shaft of the rotary shaft encoder by hand while simultaneously attempting to observe the output on the oscilloscope. Such a test procedure is often a jerry-rigged affair with the supply voltages and the outputs being connected in a rat's nest of wires. This leads to the introduction of external noise or static and to unreliable connection to the rotary shaft encoder. In addition, it is impossible to reliably turn the shaft encoder in a manner enabling the proper observation of its output when using this technique. Lastly, the outputs of the rotary shaft encoder are not loaded in the same manner as they would be loaded when employed in the controlled machine. It is possible for the outputs of the rotary shaft encoder to appear correct when tested in this manner, whereas the rotary shaft encoder will fail when required to drive the load in the controlled machine.
I n view of the foregoing it would be advantageous in the art to provide a manner for reliably and easily testing rotary shaft encoders on the workshop floor.
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USPTO Backgrounds