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EP-4313707-B1 - METHOD FOR CONTROLLING AN ADAPTIVE CRUISE CONTROL

EP4313707B1EP 4313707 B1EP4313707 B1EP 4313707B1EP-4313707-B1

Inventors

  • IDLIMAM, YOUNES
  • MANCEUR, MALIK
  • HECKETSWEILER, THIERRY

Dates

Publication Date
20260513
Application Date
20220201

Claims (9)

  1. Method for controlling an adaptive cruise control of a motor vehicle equipped with a braking system (3), in which an engine torque setpoint (CC) is delivered to the engine and a braking setpoint (CF) is delivered to the braking system (3) limiting vehicle drag, time monitoring of the engine torque setpoint (CC) and/or of a wheel torque (CR) actually produced over time being performed, characterized in that at least one maximum threshold of engine torque setpoint (CC) and/or engine torque at the wheel (CR) actually produced is determined, with, as soon as an engine torque setpoint (CC) and a braking setpoint (CF) are launched in parallel and said at least one maximum threshold is exceeded, a time counting being initiated and, if a predetermined maximum duration of parallel launching of the setpoints with exceeding of said at least one maximum threshold is reached during the time counting, a degraded mode of operation of the adaptive cruise control is implemented with cancellation of the engine torque setpoint (CC), the predetermined maximum duration of parallel launching of the setpoints (CC, CF) and exceeding of said at least one maximum threshold being experimentally calculated beforehand as a function of a maximum acceptable heating of the braking system (3) reached during the time counting duration.
  2. Method according to the preceding claim, which is implemented for motor vehicle speeds lower than 15 km/h.
  3. Method according to the preceding claim, in which the predetermined maximum duration of parallel launching of the setpoints (CC, CF) and exceeding of said at least one maximum threshold is between 25 and 35 seconds.
  4. Method according to any one of the preceding claims, in which the maximum acceptable heating is measured according to a power dissipated by the braking system (3) taking into account the motor vehicle speed, a gear ratio implemented in the motor vehicle and the engine torque setpoint (CC).
  5. Method according to the preceding claim, in which the maximum acceptable heating corresponds to a dissipated power of 7,200 Watts per wheel of the motor vehicle with an interval of ±20% around this value for a motor vehicle speed of 15 km/h, a first gear ratio and an engine torque setpoint (CC) of 600 Newton-meters.
  6. Method according to any one of the preceding claims, in which said at least one maximum threshold is equal to 840 Newton-meters with an interval of ±30% around this value.
  7. Motor vehicle comprising a powertrain (2), a braking system (3), an onboard electronic control unit (1) and an adaptive cruise control, the electronic control unit (1) comprising means for establishing an engine torque setpoint (CC) intended for the powertrain (2) and a braking setpoint (CF) intended for the braking system (3), characterized in that the electronic control unit (1) implements a method for controlling the adaptive cruise control according to any one of the preceding claims, the electronic control unit (1) comprising a time counter initiated as soon as an engine torque setpoint (CC) and a braking setpoint (CF) are launched in parallel and said at least one maximum threshold of engine torque setpoint (CC) and/or engine torque at the wheel (CR) actually produced is exceeded, means for storing a predetermined maximum duration of parallel launching of the setpoints (CC, CF) and said at least one maximum threshold and means for cancelling the engine torque setpoint (CC) when comparison means determine that a time count is greater than the predetermined maximum duration.
  8. Motor vehicle according to the preceding claim, in which the electronic control unit (1) integrates an electronic stability control system of the vehicle, the stability control system comprising a hydraulic unit ensuring transmission of the braking setpoint (CF) to the braking system (3) of the motor vehicle.
  9. Motor vehicle according to any one of the two preceding claims, in which the powertrain (2) comprises an engine control unit comprising means for monitoring the engine torque at the wheel (CR) of the motor vehicle actually produced and communicating with the electronic control unit (1).

Description

Technical field of the invention The present invention relates to a method of controlling an adaptive cruise control of a motor vehicle and to a motor vehicle comprising an on-board electronic control unit for implementing such a method of controlling the adaptive cruise control. Previous art It is known from the prior art to equip a motor vehicle with adaptive cruise control that automatically adjusts the vehicle's speed to maintain a safe following distance. Such cruise control typically uses radar, positioned at the front of the vehicle, to detect the speed and distance of any vehicle ahead. Such adaptive cruise control is known, for example, from the document EP 1971511 B1 . Furthermore, the state of the art is known from the documents WO2007006659A1 And FR3071461A1 . Since a safe following distance is predetermined by the cruise control system, if the vehicle in front slows down, the cruise control system of the vehicle behind sends a signal to the engine and/or braking system of the vehicle behind to decelerate. Then, when the road is clear, the adaptive cruise control accelerates the vehicle back to a predetermined speed. In another situation, adaptive cruise control can brake the motor vehicle when it is going downhill, therefore also outside of cases where a target is being followed. An electronic control unit installed in the vehicle operates the adaptive cruise control. The electronic control unit delivers a torque command to the engine, via an engine control unit integrated into the powertrain. Currently, adaptive cruise control is often paired with an automatic emergency braking system that enables obstacle avoidance and emergency braking to prevent accidents, particularly in urban areas. Adaptive cruise control can also be linked to the vehicle's electronic stability control system, which may also be integrated into the electronic control unit. It follows that in certain driving situations, particularly at low speeds, for example but not limited to speeds below 15km/h, a torque command to the engine and a braking command can be issued simultaneously. However, if a braking system is used excessively and for prolonged periods, the braking system can wear out more quickly and be subjected to overheating which is disadvantageous to its proper functioning; brake pads subjected to excessive heat can, for example, lose their coefficient of friction. Therefore, the problem underlying the invention is, in a motor vehicle equipped with adaptive cruise control, to no longer put such intensive stress on the vehicle's braking system under conditions of required slowing of the motor vehicle. Summary of the invention To this end, the present invention relates to a method for controlling an adaptive cruise control system of a motor vehicle equipped with a braking system, wherein a torque command is issued to the engine and a braking command is issued to the braking system, limiting vehicle drag. Time-based monitoring of the engine torque command and/or the actual wheel torque is performed. The method is characterized in that at least one maximum threshold for the engine torque command and/or the actual wheel torque is determined. As soon as an engine torque command and a braking command are issued in parallel and this maximum threshold is exceeded, a timer is initiated. A predetermined maximum duration of parallel execution is reached. If the instructions exceed at least one maximum threshold during the time count, the adaptive cruise control is operated in a degraded mode with cancellation of the engine torque instruction, the predetermined maximum duration of launch in parallel with the instructions and exceeding of said at least one maximum threshold being previously experimentally calculated based on a maximum acceptable heating of the braking system reached during the time count. Such monitoring of engine torque and braking instructions helps to prevent overheating of parts of the braking system linked to a wheel of the vehicle and subjected to the greatest heat, for example the brake discs. The occurrence of this overheating represented the most significant drawback of adaptive cruise control and could compromise vehicle safety. Therefore, a functional range for adaptive cruise control is provided, recognized as detrimental to the vehicle, where the engine torque command is overridden and the adaptive cruise control's operation is limited due to the unsafe driving conditions without this limitation. The engine torque at the wheel may differ from the engine torque target, and monitoring this difference allows for fine-tuning the adaptive cruise control. Therefore, relying solely on the engine torque target could provide an inaccurate reading, hindering the proper operation of the adaptive cruise control. When either the engine torque at the wheel and/or the engine torque setpoint are too high relative to the creep speed, it is necessary to proceed as quickly as possible to operate in degraded mode of t