RoboteQ AX2550/2850 user manual Command Control Curves, Exponentiation curves

General Operation

Command Control Curves

The AX2500/2850 can also be set to translate the joystick or RS232 motor commands so that the motors respond differently whether the joystick is near the center or near the extremes.

The controller can be configured to use one of 5 different curves independently set for each channel.

The factory default curve is a “linear” straight line, meaning that after the joystick has moved passed the deadband point, the motor’s speed will change proportionally to the joy- stick position.

Two “exponential’ curves, a weak and a strong, are supported. Using these curves, and after the joystick has moved past the deadband, the motor speed will first increase slowly, increasing faster as the joystick moves near the extreme position. Exponential curves allow better control at slow speed while maintaining the robot’s ability to run at maximum speed.

Two “logarithmic” curves, a weak and a strong, are supported. Using these curves, and after the joystick has moved past the deadpoint, the motor speed will increase rapidly, and then increase less rapidly as the joystick moves near the extreme position.

The graph below shows the details of these curves and their effect on the output power as the joystick is moved from its center position to either extreme. The graph is for one joy- stick only. The graph also shows the effect of the deadband setting.

				% Forward
				(Motor Output)
				100
				80				Logarithmic Strong
				60				Logarithmic Weak
								Linear (default)
				40				Exponential Weak
				20				Exponential Strong
- 100
	- 80	- 60	- 40	- 20				% Command Input
				0
					40	60	80	100
				20
				20
								Deadband
				40
				60
				80
				100
				% Reverse

FIGURE 16. Exponentiation curves

42 AX2500/2850 Motor Controller User’s Manual Version 1.7. February 1, 2005