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Dithering Drill for Efficient Drilling

The purpose of this investigation was to determine if we could enhance drilling capabilities in different classes of materials by perturbing speed and power. Applications of a drill that is capable of using feedback control to optimize feeds and speeds depending on the material has many application, such as drill depth for orthopedics, material removal rates for manufacturing, increasing lifespan of tool bits, but my favorite is the idea of using it in a fab lab environment for Makers.

The results of this project are summarized in the paper here.

By perturbing the voltage (varying drill speed/torque) and measuring the velocity into the material and the current of the drill, we could use system identification techniques to determing characteristic of the drill that can help us identify the type of material we are drilling into.

The drill was ziptied to a 0.5 inch plywood that was mounted with 80-20 bars. The bars created a sled that slid towards the drill and held the sample being drilled. Two constant force springs on either side ensured all trials were repeatable.

A webcam with a matlab script tracked the sled to determine drill speed. Current and Voltage probes sampled the response of the drill drulling through various materials. The drill trigger was removed to access the power transistor. A power supply (not the drill battery) was used to power the drill. The stochastic perturbation was done through an arduino script.