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Movement System Overview. The M.A.C.S. needs to be able to move up to 5mph with its self load and an additional load of up to 25lbs. The basket portion must be able to be raised and lowered +/- 6” The movement control must have enough granularity so that the movement is smooth.
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Movement System Overview The M.A.C.S. needs to be able to move up to 5mph with its self load and an additional load of up to 25lbs. The basket portion must be able to be raised and lowered +/- 6” The movement control must have enough granularity so that the movement is smooth. The M.A.C.S. should be able to perform 90 degree turns
What are the Risks? Batteries drain too quickly Motor control is jerky Motors have difficulty turning M.A.C.S cannot reach the desired speed Motor controller circuitry cannot handle the load Basket weight is difficult to raise Cost of control circuitry
Risk Mitigation Oversize batteries and motor controller current rating for longer and cooler operation Linear actuators can lift a surprising amount and should not be a limitation PWM as motor control gives us the granularity needed to make speed changes and turning smooth Gear the motors so that M.A.C.S moves 3mph at the motors’ peak efficiency RPM
Why Wheelchair Motors? Free Designed to move heavy loads Designed to run off battery power Can operate at different RPM Often have control circuitry built in
Testing Strategy (Movement) • Verify that the M.A.C.S can hold a 3mph speed with both the minimum and maximum load • Verify that the linear actuator moves the basket +/- 6” with the minimum and maximum load • Verify that 90 degree turns can be completed with the minimum and maximum load • Hold 3mph with maximum load for a minute. Measure battery drain and extrapolate for total lifetime. Also ensure PWM circuitry is within operating temp after the one minute drive. • Walk from a stop up to 5mph and back down to a stop. Verify that that speed adjustment appeared smooth
Uncertainties Cost: If we need to incorporate two PWM controllers (one for each motor) then the cost begins to become prohibitive.