Quote:
Originally Posted by GeeTwo
Also, I recall a linear accelerator that I rough-designed for Aerial Assist that used a motor and gearbox, two linkage arms, and an angled glide with a basket that the ball sat in. The point of the two-armed linkage was to match impedance between a motor/gearbox running at a constant speed and a load which was accelerating. ..... I'll look for the drawings and spreadsheet this evening.
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I was unable to locate the original drawings and spreadsheet, but I have re-generated them in the attached document.
The linkage arm connected to the motor/gearbox is 7 units long, the shaft of the motor/gearbox is 11 units perpendicularly away from the glide rail, and the secondary linkage arm is 20 units long. The "layout diagram" shows what the linkage arms will look like for each 20 degrees of rotation of the gearbox. The position-speed-accel-power shows these curves as a function of angle through the cycle, assuming that the motor/gearbox is rotating at constant speed, the mass of the load is constant, and motion is horizontal. The goal in designing the offset and linkage lengths was to produce a flat "power" curve that covered as many degrees as possible without requiring too much acceleration (and likelihood of jamming) on the return stroke. This one gives a nearly flat power curve from 40 degrees to 160 degrees. Note that the "power" for the braking and return stroke are shown as being about six times as high as the main forward stroke; however, I am assuming that the load being thrown will be several times heavier than the carriage, and that the rail will be angled (presumably at somewhere near 45 degrees), so the actual power output is much closer to a constant. If you use encoders, you can select the throwing range simply by setting a constant rotation speed for a PID loop, so it should easily scale down to lighter loads than its peak.
If you provide a desired maximum load and launch speed/throw range, I'd be happy to figure out the appropriate motor requirement, gear ratios, and arm lengths to achieve it.
And to repeat - I have not built this yet.