The modes determine how the command input (+/-10V) is interpreted.
Torque Mode: The input commands a motor torque. -10V = 100% CCW torque, 0V = zero torque and +10V = 100% CW torque. Torque is continuously adjustable over the entire range (Ex: +4.95V commands 49.5% CW torque). Almost always Torque Mode is used in CNC applications; the controller issues torque commands to the amplifier to close a PID servo loop.
Velocity Mode: The input commands a motor RPM. -10V = 100% CCW RPM, 0V = zero RPM and +10V = 100% CW RPM. RPM is continuously adjustable over the entire range (Ex: +4.95V = 49.5% CW RPM). Normally Velocity Mode is used for speed control.
Position Mode: The input commands a motor position. -10V = 100% CCW position, 0V = zero position and +10V = 100% CW position. Position is continuously adjustable over the entire range (Ex: +4.95V = 49.5% CW position). Lets say you have a 20" long linear feedback potentiometer and call the zero position mid-scale. Then -10V = -10", +10V = +10".
Mariss