Abstract: A rear wheel steering system in which the rear steering command is retrieved from a three dimensional (3D) lookup table as a function of both front wheel steering angle and vehicle speed in normal operating modes, and from a two dimensional (2D) lookup table as a function of front wheel steering angle without regard to the vehicle speed under conditions where the vehicle speed information is deemed not credible. If the measured vehicle speed is judged to be not credible, it is replaced with an estimated or recently measured credible vehicle speed value, and the replacement value is then used in connection with the measured front wheel steering angle signal to retrieve a rear wheel steering command from the 3D lookup table. However, when the front wheels have been returned to the straight ahead position, the rear wheel steering angle command is retrieved from the 2D lookup table as a sole function of the measured front wheel steering angle.

Abstract: A noncontacting automotive steering angle sensor involving the application of a two element magnetoresistive sensor to an otherwise conventional rack and pinion steering system. The rack is directly coupled to the steerable wheels, and the sensor is integrally mounted in a spring-loaded rack contacting mechanism (contact shoe) used to maintain a meshing engagement between the pinion and the rack. A variable permeability surface is formed on the surface of the rack along the travel path of the sensor such that axial movement of the rack differentially varies the magnetic flux density detected by each element of the sensor. A detector circuit comprising a bridge or simple voltage divider responsive to the differential resistances of the sensor elements develops an electrical signal indicative of the rack position.

Abstract: The gain of a servomotor driven process control system is adaptively compensated for changes in the motor coulomb friction torque. The gain is manually adjusted at the time of installation. Thereafter, the minimum motor current occurring in a process cycle is identified, and the gain is automatically adjusted if the identified minimum motor current changes over time, indicating a change in the motor coulomb friction torque. As a result, the level of response stability achieved at the time of installation is maintained despite changes in the motor coulomb friction torque.

Abstract: A torque transducer senses the operator exerted steering torque and provides an output signal which varies in magnitude from a low value representative of a large operator exerted steering torque in one direction through a mean value representative of no operator exerted steering torque to an upper limit value representative of a large operator exerted steering torque in the opposite direction. The controller develops a zero torque reference which has an initial value substantially corresponding to the mean value of the torque transducer output signal, and steering torque assist is developed in relation to the difference between the zero torque reference and the transducer output signal. In operation, the zero torque reference is shifted according to a predetermined time response characteristic in a direction to reduce the difference between it and the transducer output signal.

Abstract: The current in each phase of a multiple phase chopper is sensed and compared to a reference overcurrent value. Any chopper phase reaching overcurrent and any chopper phase on for a longer period of time are turned off immediately. The conduction periods of chopper phases that have been on for a shorter period of time than the overcurrent phase are similarly shortened to maintain balanced phase conduction and minimize the ripple content of the source current. The phase relationship among the various chopper phases is adjusted in response to an overcurrent turn-off to allow the commutation network associated with such phase to be adequately charged before the generation of a current turn-on for another phase.

Abstract: A multiple phase SCR chopper controller for establishing a normal phase relationship among the various SCR phases and for modifying the normal phase relationship for input signals for which the SCR commutation networks cannot be sufficiently charged. These input signals correspond to conduction period overlap, and the modified phase relationship avoids chopper commutation failure under such conditions.