Motor Control For the Sieg Defense Platform by Michael Dougherty Gary Look Gene Ma Reviewed by Ngochan Nguyen, Duy Le, Valdis Riekstins

Description Once given a new x-value for the x-coordinate motor, this control is responsible for providing the stepper motor driver chip with the needed signals to move the stepper motor to this position. There is another control corresponding to the motor for the y-coordinate. There is a slight difference in scaling between the x and y controls.

Stepper Motor Driver Chip The stepper motors require 0.5 mA to be driven, which the XESS board cannot provide. This chip receives signals from the motor control module, so that it can drive the motor. The chip drives the motor at 5 V.

Stepper Motor Driver Chip Inputs CLK (pin 7) - Generated by the motor control module CW/CCW (pin 10) - When low, the stepper motor is driven clockwise (right), and when high, the motor is driven counter-clockwise (left)

FPGA Signals Inputs TOUCHX[8:0] - x-coordinate to move the motor to RST - reset the x-coordinate motor to 256 (the x-coordinate range is 0 to 512) CLK - clock signal from the FPGA Outputs MotorX[15:0] - current x-coordinate of the motor MotorCon[1:0] - outputs to the Stepper Motor Chip (MotorCon[1] is CW/CCW, MotorCon[0] is CLK

How It Works The motor control keeps track of the current coordinates and also outputs them, so that a crosshair can be displayed on the screen. If the input x-coordinate is less than the current one, the motor control tells the driver chip to move the motor counter-clockwise (left), and for greater than, it tells it to move the motor clockwise (right). There is a mapping between the number of pixels between 2 points on the screen, and the amount of stepper motor movement for the corresponding distance.

Scaling Factor It takes 200 steps to move the motor 360 degrees For example, if there are 5 feet between 2 points, and it takes 90 degrees of movement to go between them

Since it takes a lot of time (in terms of clock cycles) for the stepper motor to physically move, a one million clock cycle delay (0.042 s) is introduced before the motor is told to move again. MotorCon[0] is connected to the CLK pin of the driver chip. Every time the chip sees a positive edge, it moves the motor half a step in the direction given by MotorCon[1].

Good Points The motor control will still work correctly when another coordinate is given before the motor has reached the previous one The delay between stepper motor signals ensures the motor has enough time to reach the correct coordinate

May Need Work The scaling factor may need to be adjusted for certain points in the screen/motor range Try to shorten the delay between motor signals as much as possible