Amongst tryptophan’s slumbering depression and returning unwanted gifts of another dreary chrism past, with step and direction the DC Servo Project marches valiantly into the new year…
Software and hardware development have converged into a practical test platform. The encoder processing loop has been converted to fast inline assembly and released under GPL. And in the following image, the test platform, consisting of a brushed servo motor, a power supply and a controller was assembled to facilitate rapid software development, research and testing.
The Motor and Power specifications of the test platform are as follows…
|Electrocraft E543||Power Supply|
Another view showing the back of the motor, the encoder and the drive. The power supplies and some bulk capacitance are tucked safely inside the box.
The Controller and Software specifications of the test platform are as follows…
And finally, that brings us to the tuning software being developed in the Processing environment. Visual tuning method is achieved by introduction of a 200 step disturbance, the resulting action is captured in SRAM with a 1kHz sample rate, passed forward through serial and plotted as position (upper) and velocity (lower).
As can be seen in the following image, the drive first overshoots and then settles out in just under 60 ms. In practical application, the possibility of such disturbance with infinite acceleration is null.
Some refinement of the PIV Algorithm is required to further reduce the settling time. As well as practical experimentation to determine the least number of modifiable coefficients and reduction through coefficient relationships. This is in effort to include the option of on-board tuning potentiometers, thereby greatly reducing setup complexity and setup time.
The software is to be released open source under GPL. The kit will be designed for DIY (some assembly required). The current hardware iteration can be found here: http://n0m1.com/2011/11/19/nomi-locus-dc-servo-kit/