Method and apparatus for determining slew rate limits and controlling dampers in a suspension system

A control module for a suspension damping control system for a vehicle body comprising:

• means for deriving a heave velocity of a vehicle body from sensed dynamic variables of the vehicle body;
• means for low pass filtering a magnitude of the heave velocity value with a first low pass filter coefficient while the magnitude is increasing and with a second low pass filter coefficient while the magnitude is not increasing;
• means for deriving a slew rate limit for a damping control command from the low pass filtered magnitude of the heave velocity of the vehicle body;
• means for generating the damping control command for at least one of the dampers in accordance with the slew rate limit;
• and
• means for applying the damping control command to the one of the dampers.

A method of controlling a damper in a suspension system for a vehicle body, comprising:

• determining an average heave velocity function for the vehicle body;
• determining a slew rate limit as a function of the average heave velocity;
• and
• limiting a damping control command to the damper in accordance with the slew rate limit, wherein the average heave velocity function is calculated in the following manner:
• Rectified heave velocity (RHV) = |heave velocity|;
• If Rectified heave velocity (RHV) > Average heave velocity (AHV), Then, AHV = INC_A * RHV + (1-INC_A) * AHV, Else, AHV = DEC_A * RHV + (1-DEC_A) * AHV, Endif;
• wherein INC_A is an increasing LPF coefficient and DEC_A is a decreasing LPF coefficient.

A computer readable medium storing a computer program for a suspension damping control system comprising:

• computer readable code for determining an average heave velocity for the vehicle body from input dynamic variables of a vehicle body;
• computer code for low pass filtering a magnitude of the heave velocity with a first low pass filter coefficient while increasing and with a second low pass filter coefficient while not increasing;
• computer readable code for determining a slew rate limit from the low pass filtered magnitude of the filtered average heave velocity;
• and
• computer readable code for generating a vehicle body damping control command limited in accordance with the slew rate limit for at least one damper in the suspension damping control system.

A method of controlling a damper in a suspension system for a vehicle body, comprising:

• deriving a relative heave velocity value from sensed relative body/wheel position sensors associated with the suspension system;
• determining a heave velocity estimate for the vehicle body by low pass filtering the relative heave velocity value to suppress content therein due to vertical wheel motion;
• determining an average heave velocity function by low pass filtering a magnitude of the heave velocity estimate;
• determining a slew rate limit as a function of the average heave velocity function;
• and
• limiting a damping control command to the damper in accordance with the slew rate limit.