decoding unit 8 is connected with an input terminal of the motor controller 4 the rotary transformer 7 locates nearby the rotor of the motor 6 for collecting the rotor angle position signals in a sampling period and outputting the rotor angle position signals to the revolving decoding unit 8 and the revolving decoding unit 8 may calculate rotor position values based on the received rotor angle position signals and output the rotor position values to the motor controller 4 the range of the sampling period is 10 100 u03bcs wherein apart from the skid control module for skid mode the motor controller 4 further comprises a normal travel control module and a brake control module which are necessary for the vehicle see fig2 it shows the activation conditions of these modules i e the working flow of the mode determination module shown as fig2 firstly according to the received rotor position values within a specified statistical duration the mode determination module may calculate the current acceleration a of the motor the rotor position values are provided by the revolving decoding unit 8 mentioned above the rotor speed may be calculated according to rotor position values and the current acceleration a may be calculated according to rotor speed values this acceleration may be positive or negative the positive value indicates the acceleration and negative value indicates the deceleration in which the range of the specified statistical duration is 3 10 sampling periods then the mode determination module may compare the calculated current acceleration a with a predetermined forward acceleration a0 and a predetermined backward.