Abstract: A system for anti-lock brake and traction control has a control circuit comprising a microprocessor on a silicon die. Inputs from several variable reluctance wheel speed sensors are multiplexed to a single channel on the same die for signal processing including diagnostics, A/D conversion, square wave generation for each sensor by a state machine, end wheel speed determination from the square waves. The state machine algorithm tracks signal peaks and valleys and uses a dual hysteresis method of generating output transitions to capture all cycles of a signal having single cycle anomalies while rejecting noise. A single rear wheel sensor having twice the frequency of front wheel sensors for equal wheel speeds is processed twice as often as each front sensor. The diagnostics include detecting sensor and harness short and open circuits by comparison of signals to programmable thresholds and fault timing and latching by gauging open and short signals against programmable time limits.

Abstract: A system for anti-lock brake and traction control has a control circuit comprising a microprocessor on a silicon die. Inputs from several variable reluctance wheel speed sensors are multiplexed to a single channel on the same die for signal processing including diagnostics, A/D conversion, square wave generation for each sensor by a state machine, and wheel speed determination from the square waves. The state machine algorithm tracks signal peaks and valleys and uses a dual hysteresis method of generating output transitions to capture all cycles of a signal having single cycle anomalies while rejecting noise. A single rear wheel sensor having twice the frequency of front wheel sensors for equal wheel speeds is processed twice as often as each front sensor. The diagnostics include detecting sensor and harness short and open circuits by comparison of signals to programmable thresholds and fault timing and latching by gauging open and short signals against programmable time limits.

Abstract: A system for anti-lock brake and traction control has a controller circuit comprising a microprocessor on a silicon die. Inputs from several variable reluctance wheel speed sensors are multiplexed to a single channel on the same die for signal processing including diagnostics, A/D conversion, square wave generation for each sensor by a state machine, and wheel speed determination from the square waves. The diagnostics include detecting sensor and harness short and open circuits by comparison of signals to programmable thresholds and fault timing and latching by gauging open and short signals against programmable time limits. Common mode noise rejection is accomplished by detecting common mode aberration and disabling an A/D converter during the aberrations.

Abstract: A vehicle controller in which inputs from several wheel speed sensors are used to compute wheel speed. A redundant circuit in the controller receives the sensor input signals and computes wheel speed in a different, software intensive, way. The primary and redundantly computed wheel speeds are compared to validate the primary controller circuitry and the portion of the controller used to process compute the redundant speed signal. To additionally verify proper calculation of wheel speed, the system is tested when the vehicle is at rest by applying an artificial sensor signal to the control input and then checking to see whether the controller determined the correct wheel speed.

Abstract: A digital timer apparatus incorporates a free running counter, an interval timer, a capture register, a pulse accumulator; holding logic and mode selection logic. In one mode of operation, a rising or falling edge of an external signal causes the current contents of the free running counter to be loaded into the capture register, causes the previous value of the capture register to be transferred to a holding register and causes the pulse accumulator to be incremented. A read of the capture holding register causes the pulse accumulator value to be transferred to a holding register and causes the pulse accumulator to be reset. The output of the interval timer can cause an interrupt signal to be generated to request service from a central processing unit.

Abstract: An ABS system has a plurality of brake channels receiving apply pressure directly from a pump without an accumulator during ABS operation. To assure sufficient pressure for all channels during ABS reapply modes the channels are multiplexed to apply one at a time and keeping on hold other channels scheduled for apply. Several states of brake application are identified and the states are prioritized for each channel so that the multiplexing is ordered according to channel priority.