Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D7/00—Steering linkage; Stub axles or their mountings
  • B62D7/06—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins
  • B62D7/14—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering
  • B62D7/15—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering characterised by means varying the ratio between the steering angles of the steered wheels
  • B62D7/159—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering characterised by means varying the ratio between the steering angles of the steered wheels characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Definitions

• a method of controlling and controlling steering of the rear wheels of a vehicle is a method of controlling and controlling steering of the rear wheels of a vehicle.
• the present invention relates to a control method of turning the rear wheels of a four-wheel steering vehicle.
• the rear wheels turn at the opposite end of the front wheels.
• the vehicle rotates as if it had a smaller apparent wheelbase than in the case where the rear wheels do not steer.
• the forward directional pattern for example common with that of the two-wheel steering vehicles, does not differentiate then as sez the steering of the inner wheel turn which shines more and the outer wheel which shines less.
• the document FR2883828 discloses a four-wheel steering vehicle with steering direction of vehicle without mechanical link between steering wheel and steering wheels so as to best respect a Jeantaud's design under constraint of a maximum transverse acceleration to meet.
• the context of this earlier document is more particularly that of high speeds.
• the object of the invention is to provide a method for controlling and controlling steering of the rear wheels on a four-wheel steering vehicle executed from a start-up stage of the vehicle to generate a setpoint of steering angle of the rear wheels.
• the process is remarkable in that it comprises:
• the temperature of at least one tire is estimated to be equivalent to an ambient temperature outside the vehicle.
• the method includes a step of verifying a vehicle stopping time greater than a predetermined duration threshold so as to execute the temperature detection step if the stopping time of the vehicle is greater than the threshold of predetermined duration and to directly execute the step of applying the first control law if the stopping time of the vehicle is not greater than the predetermined duration threshold.
• the temperature threshold is equal to a temperature value of between 3 ° C. and 6 ° C.
• the second amplitude limitation is zero within a second speed range contained in the first range of vehicle travel speeds.
• the second amplitude limitation is equal to the first amplitude limitation, for any speed of movement of the vehicle outside the first speed range.
• the method comprises, following the step of applying the second control law, a step of maintaining the second control law as long as at least one pre-established condition is not satisfied to sufficiently increase the temperature of at least one tire above the temperature threshold.
• At least one pre-established condition is considered satisfied when the vehicle has traveled a predetermined distance.
• the method comprises, following the step of maintaining the second control law, a step of detecting a steering angle zero before, to initiate the step of applying the first control law.
• the invention is also directed to a computer program comprising program code instructions for carrying out the above described method steps.
• the invention is obj and a four-wheel steering vehicle comprising at least one on-board computer configured to execute the above-mentioned program.
• the invention makes it possible in cold weather, for example below 5 ° C for the tires, to reduce the freezing of the tires so as to reduce, or even eliminate, the unpleasant effect of twisting the nose gear, or at least to bring it back at the level of that of a two-wheel steering vehicle, significantly less affected by the phenomenon.
• FIG. 1 shows process steps according to the invention for controlling the steering of the rear wheels
• FIG. 2 is an explanatory diagram of a device for implementing the method of FIG. 1;
• FIG. 3 is an example of a control law to which the invention is applicable
• the aim of the method according to the invention is to carry out a steering control of the rear wheels on a four - wheel steering vehicle executed from a step 100 of starting the vehicle.
• the start step 100 activated at the start of the vehicle, triggers a step 101 of checking the duration during which the vehicle has stopped before starting.
• Step 101 triggers a tire temperature detecting step 102 following step 100, preferably but not necessarily only if the vehicle has been stopped beyond a predetermined time threshold before starting. .
• the duration threshold is predetermined experimentally or by calculation in the design and test phases of the vehicle until sufficient cooling of the tires or other components of the vehicle is achieved, to substantially reach the temperature outside the vehicle which corresponds to the ambient temperature.
• warming up of the tires or other parts of the vehicle while taxiing before the stop is extremely variable depending on various factors such as the duration, the driving speed, the temperature tire inflation and many other known factors. Therefore, the time required to obtain sufficient cooling of the tires to substantially reach the temperature outside the vehicle, is also variable.
• the duration chosen is that which, during tests, makes it possible to reproduce the unwanted twitching phenomenon with sufficient certainty.
• a time duration of one hour is generally well beyond that sufficient to obtain good cooling, able to cause the jolt.
• a dedicated time counter can be provided in an on-board computer of the vehicle executing the method.
• Step 103 consists of applying a first control law which we now explain by relying on a device 10 for generating a steering angle setpoint or of the rear wheels of the vehicle, as illustrated in FIG. 2.
• the device 10 comprises an input module 11 which receives a steering angle setpoint ov of the front wheels of the vehicle and an output module 12 which generates the steering angle setpoint oiar rear wheels based on the steering angle set ov of the front wheels.
• the steering angle setting o v of the front wheels may result from a rotation angle measurement of a steering wheel of the vehicle or a steering rack position measurement.
• the setpoint steering angle o v of the front wheels can also be a set generated by the automation.
• the input module 11 develops a steering angle functional setpoint af which is, for example, proportional to the angle of airset pointer C (Xav of the front wheels in a ratio AR / AV varying according to the speed v of the vehicle as shown in Figure 3.
• the rear wheel turning ratio AR / AV of the front wheels is generally zero for speeds ranging from zero to a relatively low speed value VI, for example of the order of 2 km / h.
• a deflection of the front wheels causes no steering of the rear wheels for a zero speed of the vehicle, even for speeds below 2 km / h.
• the steering ratio AR / AV is for example equal to -0.3 to increase gradually, that is to say decrease in absolute value, to zero for a speed value V5 of the order of 60 km / h, knowing that the value of V5 can vary from one type of vehicle to another or a selected driving mode to another.
• the steering ratio AR / AV becomes positive and continues to increase progressively as a function of the speed without, however, exceeding a value of, for example, 0.2.
• the rear wheels turn in the same direction as the front wheels so as to prevent the rear portion of the vehicle to drive out of a turn approached high speed.
• the AF functional instruction is not directly applicable to the rear steered wheels for a variety of reasons, among which there may be mentioned a physical limitation of the steering actuators of the rear wheels, stability constraints of the vehicle or others.
• the output module 12 generates the steering angle setpoint a ar of the rear wheels based on the steering angle setpoint a front wheel av by limiting the value af as explained now with reference to Figure 4.
• the graph of FIG. 4 also shows in abscissa values in km / h of speed v of the vehicle, but differently on the ordinate of the values in angular degrees of limitation of amplitude LIM (a ar ) of the steering angle set age a a r rear wheels.
• the dashed curve 1 gives zero limiting values of the steering angle setpoint a ar of the rear wheels, inside. speed ranges between zero and VI and for the speed value V5 which corresponds to the change of sign of the steering angle a ar of the rear wheels, of opposite sign to that of the front wheels for low speeds and of the same sign for high speeds.
• the limitation is of maximum amplitude in absolute value, here at substantially 3.5 ° opposite to the steering angle of the front wheels.
• the limitation gradually increases in absolute value, from 0 ° to substantially 3.5 °.
• the amplitude limitation gradually decreases in absolute value, from 3.5 ° to 0 °.
• the limitation LIM (aar) increases progressively in the same direction as the steering angle of the front wheels, until it saturates at approximately 1 ° well before reaching a speed of 200 km / h.
• the output module 12 For the same speed V4 of the order of 20 km / h, by applying the limitation of the curve 1 to the steering angle functional setpoint af, the output module 12 generates a steering angle setpoint a rear wheel angle equal to -1.25 ° for a steering angle setpoint ov of + 5 °, and equal to -3.5 ° for a setpoint angle of braking angle C (Xav + 20 °), which gives a value of a ar in an acceptable pattern It will of course be understood that conversely, at the same speed of 20 km / h, the output module 12 generates a steering angle setpoint a ar of the rear wheels equal to + 1 , 25 ° for a steering angle setpoint at av of -5 °, and equal to + 3.5 ° for a steering angle setpoint at av of -20 °.
• the law of evolution of the functional specification af steering angle, affecting the proportionality coefficient F / R of Figure 3 the steering angle set has av front wheels is only given as non-limiting example.
• the invention is applicable to any other evolution law such as, for example, a law of polynomial evolution of the steering angle functional setpoint af, or any other evolution law taking as input the steering angle setpoint ov of the front wheels.
• the invention is still applicable to a steering angle af functional specification no direct connection with the steering angle set has av of the front wheels, for example in the case of a self-driving vehicle for which higher level optimization algorithms directly generate a steering angle function set af rear wheels. In such a case, the input module 11 of the device 10 is useless, the steering angle functional setpoint af further developed directly attacking the output module 12
• the invention focuses on the amplitude limitation that we detail now.
• Step 102 is to detect whether the temperature of at least one tire is below a temperature threshold.
• a tire temperature could be measured by means of a sensor disposed against, on one or more wheels.
• the tire temperature then measured in real time at each instant, would make it possible to trigger step 102 or not without having to check the stopping time preceding start-up, but the execution performance of the process thus obtained does not necessarily justify the additional cost generated by the installation of these sensors.
• the temperature of at least one tire estimated to be equivalent to the temperature outside the vehicle saves the cost of the sensors, their assembly and the processing of their signals.
• the temperature outside the vehicle is generally available on the on-board network for other purposes, for example for display on the dashboard. This estimate is sufficient for an all-to-one execution is acceptable, knowing that the temperature of a tire is substantially equivalent to the ambient temperature, as long as the vehicle has not traveled a sufficient distance to cause appreciable heating.
• the temperature threshold is optimal, the one below which the tires do not have sufficient flexibility to absorb the shifts of wheels on very short turning radii, in other words for high steering angles on the front wheels while the steering, also high, the rear wheels comes to disrupt the respect of the purity of Jeantaud. It will be understood that the temperature threshold depends not only on the type of tire but also on its age, its state of inflation or the pavement of the roadway. The optimum temperature threshold may therefore vary from one vehicle to another. We could consider a self-learning mechanism that would set a new value of the temperature threshold as soon as chatter occurs on the front wheels so as to avoid a reappearance of the phenomenon.
• a threshold equal to a temperature of 4 ° C. in a tolerance range of plus or minus two degrees Celsius, for example with a value of 5 ° C. makes it possible to give an acceptable level of satisfaction.
• the optimal threshold is 1 ° C
• no unnecessary execution of four-wheel drive implementation clamping steps will take place for temperatures above 5 ° C, thus leaving the user fully benefit from its four-wheel steering for temperatures above the threshold as soon as possible. the first meters of rolling.
• the method consists of the step 103 of applying the first control law which is the normal control law of the rear steered wheels for the driving mode selected by the driver or the user of the vehicle in the case of a self - driving vehicle, for example from a normal, economic or even sport or comfort mode.
• the first control law which is the normal control law of the rear steered wheels for the driving mode selected by the driver or the user of the vehicle in the case of a self - driving vehicle, for example from a normal, economic or even sport or comfort mode.
• the method consists in applying a second control law possibly based on, but in any case different from the first control law.
• This second control law includes a second limitation in amplitude of the steering setpoint of the rear wheels which is lower in absolute value than the first limitation of the first control law, within the first range of speeds its VI, V4 moving the vehicle as shown in Figure 4.
• Different ways can be used to position the second limitation to a lower value in absolute value than that of the first limitation, for example to a percentage of that of the first limitation over a range of speeds VI to V3 where V3 is a speed lower than V4.
• V3 is a speed lower than V4.
• the speed V3 could be between 1 5 and 1 8 km / h depending on the value of the percentage so as to crawl the second limitation between its value at speed V3 and its value at the speed V4 from which the second limitation becomes equal to the first limitation.
• the second limitation could also be implemented equal to the first limitation for the velocities below the velocity e VI and then crawled from zero to the value of the first limitation over the range of its velocities between VI and V3 and then equal to the first limitation for speeds faster than speed V3.
• the second limitation 3 in phantom in FIG. 4 is equal to a percentage of the first limitation 1 over a range of speeds from V3 to V4 and then constant beyond V4 to rejoin the first limitation. 1 for a value of speed beyond which, the limitation 3 merges with the limitation 1.
• the second limitation 2 of steering of the rear wheels is zero within the range of speeds between V I and V3 contained in the range of its V I to V4 vehicle travel.
• a first speed range between a speed of 2 km / h and a speed of 20 km / h
• a second speed range between a speed of 2 km / h and a speed of V3 of 15 km / h. km / h is contained in the first speed range.
• the second limitation 2 of the steering position of the rear wheels is then equal to the first limitation 1 of turning of the rear wheels steering of the front wheels, for any speed v of movement of the vehicle outside the first speed range VI, V4.
• the second steering limitation 2 is then ramped from zero to the value of the first at the speed V4 to avoid a sudden change in the second limitation 2 before reaching the speed V4.
• the zeroing of the second limitation 2 for vehicle velocities less than or equal to V3, for example but not necessarily of the order of 1 5 km / h, allows a particularly simple implementation of the method. It consists for example simply to deactivate the four-wheel steering mode for vehicle speeds below V3, activating only the steering of the two front steering wheels.
• a first alternative embodiment could be to return to step 102 to again detect the temperature of the tires so as to restart in step 103 or in step 104 depending on the value of detected temperature.
• This first alternative requires at least one temperature sensor on the wheel because in rolling the outside temperature is no longer representative of the temperature of the tires.
• a step 105 consists in maintaining the second control law as long as at least one pre-established condition is not satisfied to sufficiently increase the temperature of at least one tire beyond the threshold .
• the pre-established condition could relate to a sufficient period of vehicle travel to increase the temperature of the tires beyond the threshold.
• the pre-established condition relates to a distance of movement of the vehicle which is sufficient to cause heating of the tires, capable of increasing their temperature beyond the temperature threshold.
• the distance is predetermined during the test phase of a prototype vehicle so as to satisfy the known terms of use of the vehicle. It was found that the adverse effect largely disappears after 100 m of rolling. The pre-established condition is then considered satisfied when the vehicle has traveled the predetermined distance.
• step 106 for detecting a flying angle zero crossing makes it possible to trigger the step 103 of applying the first control law when it is no longer necessary to apply the second law of command.
• a computer program comprising program code instructions for executing the steps of the method described above, when the program is executed on a computer.
• the four-wheel steering vehicle then comprises one or more embedded computers configured to perform the planned program.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mathematical Physics (AREA)
• Theoretical Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Steering Control In Accordance With Driving Conditions (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=61132546

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• 2017
  • 2017-10-20 FR FR1759884A patent/FR3072631B1/fr active Active
• 2018
  • 2018-10-15 EP EP18786758.5A patent/EP3697673A1/de not_active Withdrawn
  • 2018-10-15 RU RU2020116373A patent/RU2020116373A/ru unknown
  • 2018-10-15 WO PCT/EP2018/077978 patent/WO2019076779A1/fr unknown
  • 2018-10-15 CN CN201880068311.8A patent/CN111247052A/zh active Pending

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