GB2580979A

GB2580979A - Method of torque and acceleration monitoring in a vehicle

Info

Publication number: GB2580979A
Application number: GB1901487.7A
Authority: GB
Inventors: Bauche Florian; Armengaud Jeremy; Vassallo Damien
Original assignee: Delphi Automotive Systems Luxembourg SA
Current assignee: BorgWarner Luxembourg Automotive Systems SA
Priority date: 2019-02-04
Filing date: 2019-02-04
Publication date: 2020-08-05
Also published as: GB201901487D0; WO2020161127A1

Abstract

Disclosed is a method of monitoring a vehicle, the vehicle including an internal combustion engine. The method comprises monitoring the acceleration of the vehicle and determining if there is excessive acceleration or not; monitoring the torque developed by the engine and determining if there is excessive torque or not; flagging or not flagging a fault condition dependent on the results. The method provides a means to rapidly and accurately determine an engine fault where acceleration deviates from the intended acceleration. In some instances if the acceleration is higher than anticipated then this could be due to the vehicle accelerating downhill and the excess toque measurement is used to eliminate this possibility. In other instances the excess torque determination can provide quicker means of detecting a fault than waiting for a measurement of the rate of vehicle acceleration. Also disclosed is a system for detecting a fault in a vehicle. The combination of the two methods of fault detection in a single system provide a more robust arrangement than either system used independently.

Description

Method of Torque and Acceleration Monitoring in a Vehicle

TECHNICAL FIELD

This relates to a method of monitoring torque and acceleration in a vehicle.

BACKGROUND OF THE INVENTION

Preventing unwanted acceleration is done currently either by acceleration based monitoring or continuous torque monitoring.

To prevent unwanted vehicle acceleration, two main methodologies are used in prior art. One is torque monitoring of the vehicle engine; this method is complex to develop and focuses only on engine torque while a slight overshoot of engine torque will have no effect on vehicle dynamic. The other is vehicle acceleration monitoring; this method is simple and is more resilient to small, irrelevant torque error. However when driving e.g. down a slope, it is not possible to differentiate between acceleration due to the slope or unwanted acceleration from the engine without adding an inclination sensor.

So many prior art systems require an inclination sensor, or monitoring air filling inside the engine along with acceleration monitoring concept. In case of excessive acceleration, for instance in a slope, actions are taken only if an excessive amount of air inside the engine is suspected.

When using acceleration monitoring or torque monitoring there is a need to set high detection thresholds for excessive acceleration detection. This leads to higher and longer excessive acceleration before system reaction Patent US9460628 describes a method and device for preventing unintentional acceleration of a motor vehicle. US6919801B2 describes a vehicle safety system for preventing inadvertent acceleration of a vehicle. US8775046B2 describes an unintended acceleration detection and correction, and US8548712B2 describes an acceleration-based safety monitoring of a drive of a motor vehicle.

It is an object of the invention to overcome these problems and include a methodology which does not include an inclination sensor.

SUMMARY OF THE INVENTION

In one aspect is provided a method of monitoring a vehicle, said vehicle including an internal combustion engine; comprising: a) monitoring the acceleration of the vehicle, and determining if there is excessive acceleration or not; b) monitoring the torque developed by the engine, and determining if there is excessive torque or not; c) flagging or not flagging a fault condition dependent on the results of steps a) and b) . The method may include the step of d) controlling said vehicle to take remedial action of a fault is flagged in step c) Step a) may comprise determining if the acceleration is above a threshold level.

Step b) may comprise determining the undershoot or overshoot of torque, comparing this with a threshold and determining excess torque bases on In step a) it is determined there is no excessive acceleration and in step b) it is determined that there is excessive torque, then step d) comprises controlling the vehicle engine to limit the torque produced.

If in step a) it is determined there is no excessive acceleration and in step b) it is determined there is excessive torque, then step d) may comprise controlling the vehicle engine to limit the torque produced.

If in step a) it is determined there is excessive acceleration and in step b) it is determined there is no excessive torque then in step c) not fault may be flagged and/or step d) no action is taken

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the 10 accompanying drawing in which: -Figure 1 shows a flow chart of the methodology according to one example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one aspect of the invention acceleration and torque monitoring is performed.

In one example acceleration based monitoring is running all the time and torque monitoring is activated only if acceleration monitoring has detected an excessive acceleration.

In case of normal driving situation, if the torque monitoring detects a small excessive torque but the vehicle acceleration monitoring does not detect excessive acceleration then the situation is safe and no action is taken. On the contrary if torque monitoring detects a high excessive torque then we can predict an excessive acceleration. The acceleration may not yet have occurred because of vehicle inertia. As a consequence, actions may be taken to limit engine torque depending on the degrees of excessive torque.

In this way a less complex torque monitoring method is provided because the inconsequential over/undershoots of torque a safety point of view will be ignored.

In case of acceleration monitoring if excessive acceleration is detected, the torque monitoring may be used to confirm the unwanted acceleration as follows if the torque monitoring does not detect any error on engine torque then it means that the car is accelerating because it is going downhill and no action to control it is necessary. On the contrary if torque monitoring detects excessive torque then the ongoing acceleration detected is indeed unexpected and actions to limit it should be taken to bring back the vehicle in a safe situation. Thanks to that strategy neither the inclination sensor is necessary anymore nor is there a need to set high detection threshold to avoid detecting downhill situation.

Figure 1 shows a flow chart illustrating methodology of the invention. Within the flowchart are shown three sub-methods which may be performed on their own.

Acceleration monitoring occur in step S1. On the left hand side of the figure in step S2 acceleration monitoring detects an excessive acceleration (i.e. above a threshold).

In one example measured acceleration is compared to expected acceleration. The expected acceleration may be measured from torque output or torque demand (in a closed loop system) along with other parameters such as vehicle mas. The skilled person would be able to determine from estimation or testing what the threshold for "excessive" may be. In examples (vehicle reaction test) curves may be utilized to determine maximum duration of an excessive acceleration before action are taken.

Subsequent or concurrent torque monitoring is performed and in step S3 there is detected excessive torque. This may be torque undershoot or overshoot i.e. the amount the actual or measured torque is away from the demand torque; (i.e. measured torque is compared to the engine demand in a closed loop control system which compares its torque output to its torque demand In this case excessive torque depends on the torque estimator we use. If e.g. torque estimation is accurate down to 10Nm; 20Nm is then a reasonable excessive torque value because we can clearly deduce that a 30Nm over/undershoot is not only caused by bad torque estimation. On the contrary with a simplified torque estimator then we might have 25Nm accuracy which means excessive torque is then 50Nm A conclusion in step S4 is that unwanted acceleration is present -excessive acceleration is caused by excessive torque. Consequently in step S5 action may be taken to limit the torque.

If there is no excessive torque after excessive acceleration had been detected at step S6 then a conclusion at step S7 may be that there is a downhill situation and excessive acceleration is caused by the downhill slope. At step S8 it is decided no consequential action is taken.

On the right hand side at step S9 no excessive acceleration if detected. The torque monitoring either detects excessive torque (e.g. above a threshold) at step S10 or no excessive torque at step S11. If there is no excessive torque then at step S12 it is assumed normal driving conditions and at step S13 it is concluded no action is to be taken.

If excess torque has been detected at S10, it is decided whether excess torque (torque overshoot or undershoot) is below or above a threshold (e.g. 50Nm). If this is below a threshold at step S14 then at step S15 the excessive torque is ignored as it is concluded that the error in torque (excess) is to small to have an impact on e.g. vehicle acceleration. At step S16 it is concluded no consequential action is to be performed.

If the excess torque (torque overshoot or undershoot) is above a threshold (e.g. 50Nm) at step S17, then it is decided at step S18 that the excessive torque is dangerous and that vehicle acceleration may soon become dangerous. At step S19 action is taken to limit the torque produced.

In contrast to the prior art this methodology does not need an additional sensor to achieve unwanted acceleration detection in all situations or a specific monitoring of engine air charge; so the advantage is that it is not using any additional sensors without infringing on safety by setting high detection thresholds.

It is also an improvement compared to the prior act as it allows a better detection of an unexpected acceleration in a context of a downhill situation. Indeed by design the torque monitoring is also taking into account the unexpected acceleration due to spark ignition timing alteration while the air charge based detection doesn't consider it.

It also eases the torque monitoring development process as it doesn't need to be active all the time. It makes it more resilient to faulty or irrelevant detection of excessive torque situation as it is used in conjunction with the acceleration monitoring