Steering control system
A steering control system for a vehicle comprising a steering input member controlled by a driver of the vehicle comprises a steering sensor for generating an electrical signal as a function of the position of the input member. The steering control system further comprises a steering actuator which operates on the steered wheels of the vehicle as a function of the electrical signal generated by the steering sensor. A steering controller receives the electrical signal generated by the steering sensor and provides a current to the steering actuator in order to operate on the steered wheels. An accumulation counter is operatively connected with the steering controller and is configured to calculate and record the accumulated workload of the steering controller by accumulating instantaneous workloads throughout operation thereof.
1 . A steering control system for a vehicle, comprising:
a steering input member;
a steering sensor configured to generate an electrical signal as a function of a position of the steering input member;
a steering actuator configured to operate on steered wheels of the vehicle as a function of the electrical signal;
a steering controller configured to receive the electrical signal and provide current to the steering actuator; and
an accumulation counter comprising at least one electronic processor and a non-transitory memory storing executable instructions which, when executed by the processor, cause the accumulation counter to: (i) determine an instantaneous workload value for the steering controller; (ii) obtain a torque value represented by the electrical signal and an operational temperature of the steering controller; (iii) determine a torque weighting factor from a first lookup table indexed by the torque value and a temperature weighting factor from a second lookup table indexed by the operational temperature; (iv) form a weighted workload unit by multiplying the instantaneous workload value by the torque weighting factor and the temperature weighting factor; and (v) integrate the weighted workload unit over time to calculate and record an overall accumulated workload of the steering controller.
2 . A steering control system according to claim 1 , wherein the instantaneous workload value of the steering controller is an instantaneous current provided to the steering actuator by the steering controller in order to operate on the steered wheels.
3 . A steering control system according to claim 1 , wherein the instantaneous workload value is determined for each incremental time unit, and the weighted workload unit is determined by applying a multiplier equal to the product of the torque weighting factor and the temperature weighting factor to the incremental time unit.
4 . A steering control system according to claim 1 , comprising a weighting circuit or processor configured to apply the torque weighting factor and the temperature weighting factor to each instantaneous workload value to provide the weighted workload unit.
5 . A steering control system according to claim 4 , wherein the accumulation counter is configured to determine an accumulation of weighted workload units to provide an overall workload of the steering controller.
6 . A steering control system according to claim 4 , wherein the torque value used to index the first lookup table is a demanded torque represented by the electrical signal received by the steering controller.
7 . A steering control system according to claim 6 , wherein the the weighting factor is proportional to the torque represented by the electrical signal.
8 . A steering control system according to claim 4 , wherein the weighting circuit or processor is configured to receive as an input an operational condition comprising the current provided to the steering actuator by the steering controller, and the accumulation counter is further configured to determine a current weighting factor from a third lookup table indexed by the current.
9 . A steering control system according to claim 8 , wherein the third lookup table is monotonic such that the current weighting factor increases with increasing current.
10 . A steering control system according to claim 4 , wherein the operational temperature is an internal temperature of the steering controller measured by a temperature sensor or estimated by the steering controller.
11 . A steering control system according to claim 10 , wherein the second lookup table is montonic such that the temperature weighting factor increases with operational temperature.
12 . A steering control system according to claim 4 , comprising an overall workload threshold.
13 . A steering control system according to claim 12 , comprising an alert circuit or controller configured to activate an alert when the overall workload determined by the accumulation counter exceeds the overall workload threshold.
14 . A steering control system according to claim 12 , further comprising a control processor configured to apply an operational limit to the steering controller when the accumulation counter determines that the overall workload is within a predetermined range of the overall workload threshold.
15 . A steering control system according to claim 12 , further comprising a temperature monitoring module configured to monitor the temperature of the steering controller and reduce the current provided to the steering actuator when the accumulation counter determines that the overall workload is within a predetermined range of the overall workload threshold and the temperature is above a predetermined threshold.
16 . A steering control system according to claim 13 , further comprising a control processor, wherein the control processor is configured to enforce an operational limit comprising a maximum current provided to the steering actuator and/or a maximum period of time during which current above a predetermined threshold is provided to the steering actuator.
17 . A steering control system according to claim 4 , wherein at least one of the first and second lookup tables is stored in the non-transitory memory of the accumulation counter.
18 . A steering control system according to claim 4 , wherein the weighting circuit or controller applies the weighting factor as a multiplier to each instantaneous workload.
19 . A steering control system according to claim 1 , wherein the accumulation counter is configured to determine the accumulated workload throughout the life of the steering controller.
20 . A steering control system according to claim 1 , wherein the steering actuator comprises a power steering motor.
21 . A steering control system according to claim 1 , for use in a steer-by-wire vehicle and wherein the steering actuator is configured to set the position of the steered wheels.
22 . A power steering unit comprising a steering control system according to claim 1 .
23 . A vehicle steering system comprising a steering control system according to claim 1 .
24 . A vehicle comprising a steering control system according to claim 1 .