Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D5/00—Power-assisted or power-driven steering
  • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D5/00—Power-assisted or power-driven steering
  • B62D5/001—Mechanical components or aspects of steer-by-wire systems, not otherwise provided for in this maingroup
  • B62D5/003—Backup systems, e.g. for manual steering
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D5/00—Power-assisted or power-driven steering
  • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
  • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
  • B62D5/0481—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such monitoring the steering system, e.g. failures
  • B62D5/0484—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such monitoring the steering system, e.g. failures for reaction to failures, e.g. limp home
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D9/00—Steering deflectable wheels not otherwise provided for

Definitions

• the present invention relates to road motor vehicles provided with a steering system of which all the steering wheels are controlled by a steering actuator of its own.
• the invention aims in particular, among the known steering systems, those which lack a mechanical connection between the steering wheels and the steering wheel and also have no mechanical connection to synchronize steering between steered wheels themselves.
• Electrical steering systems comprising an individual electric actuator for a steering wheel, the steering system being capable of selectively steering each of the steering wheels by an angle that is specific to it, the consistency of the steering forces of each of the steered wheels. being ensured by the control electronics.
• the electric actuator of each wheel has the function of imposing on the wheel considered the steering angle chosen by the steering electronics.
• the steering control available to the driver of the vehicle may be a traditional steering wheel or joystick like a joystick or other suitable device.
• the orders printed by the driver of the vehicle on his control device are sent to the control electronics loaded with appropriate programs to be able to control the actuator (s) in an appropriate manner.
• One of the advantages of this technology is that it blends ideally with electronics and computers, the progress of which allows more and more sophisticated servocontrols, which makes it possible to place the wheel turning not only under the control of the manual control but also under the control of a security system.
• an angle can be imparted to the steering wheels that takes into account not only the control of the driver of the vehicle, but also takes into account the dynamic parameters observed on the vehicle.
• the electric steering it opens a field of possibilities much wider to act on the stability of a vehicle's trajectory.
• an automatic system for correcting the trajectory of the vehicle prints corrective laces moments by means of the brakes of one or more wheel
• the transition to electrical controls of the various functions on a vehicle would act on the steering angle of the different steering wheels of the vehicle to correct the trajectory.
• the steering system of a vehicle is an essential and vital function for safety, such as the brakes. Therefore, to be able to replace the mechanical directions, assisted or not, almost universally adopted at present on all road vehicles, it is essential that an electrical steering system is extremely safe. This is why redundant electrical systems are generally designed to enable system operation even if one of its components fails. This is the concept of fault-tolerant system. All functionality is provided in case of failure of one of the system components, or at least those deemed most important. Thus, for example, the electrical parts of the wheel actuators are preferably redundant. For example, see patent application US 2003/0098197 giving an example of a redundant system for controlling an electrical direction.
• US Pat. No. 5,014,802 discloses a steering system for a four-wheel-drive vehicle, which proposes, when a first steering wheel reaches the steering stop and the driver wishes to increase the steering further, Jeantaud's plan to avoid wheel slippage on the ground in all turning circumstances.
• the inventors have planned to apply the invention to a system where all the wheels are individually controlled, the possibility of failure and the strategies to be adopted in this case remain completely foreign to this description.
• an electric wheel actuator may fail such that it assumes an indifferent angular position, a situation in which it is unable to transmit steering (or keeping straight) forces. Or it can remain locked in a certain angular position, for example in a straight line, due to mechanical damage. This is the case of the blocking of an actuator that deals with the present patent application.
• patent application US 2004/0140147 proposes to control the other wheel actuator of the same axle according to a modified angular position instruction, so that overall the axle develops a transverse thrust as little different as possible thrust that one would have obtained without failure of actuator.
• This solution has the disadvantage of causing the appearance of antagonistic constraints, especially in tires. It is therefore desirable to adopt it only as a last resort. There remains a need to find solutions that make it possible to cope with the blocking of an electric actuator without developing such antagonistic efforts.
• the object of the invention is therefore, in case of impossibility of changing the steering angle of a steering wheel, to maintain as much as possible control of the path of the vehicle according to the wish of his driver, preferably without skidding the wheels, at least so that the vehicle can be stored where its passengers are safe.
• Another object of the invention is to, when it proves impossible to avoid the shifting of the wheels, can still adopt a steering strategy steering wheel unblocked most appropriate to the situation for the less able to stow the vehicle where its passengers are safe.
• the invention proposes a steering system for a land vehicle with at least four steering wheels, the system comprising a steering wheel actuator, the system comprising a real steering angle sensor of each of the steering wheels, the system comprising a control member at the disposal of a driver and delivering a requested steering angle, said steering system comprising a steering control unit using as input variable at least said requested steering angle to determine a steering angle.
• the system comprises means for detecting a blockage of one of the steering wheel actuators, said means being capable of delivering, in the event of a detected blockage, an alert signal identifying the locked actuator, said steering control unit having at least one normal mode and at least one degraded mode in case of blockage e of an actuator, the degraded mode calculating the steering angle of the steering of unblocked wheels by imposing a first degraded mode strategy by which the instantaneous center of rotation of the vehicle is located substantially on the line perpendicular to the plane of the wheel blocked and passing through the center of the ground contact area of the locked wheel, at a position depending on the required steering angle.
• degraded mode All the functionalities are no longer assured, but the vehicle's operational safety is best ensured according to the circumstances.
• the degraded mode will allow operation of the vehicle steering system certainly less pleasant, but avoiding any tragic consequences for the passengers of the vehicle.
• the electric actuator directions also meeting the characteristics indicated in the preamble above, provide a preferred field of application of the invention.
• hydraulic steering systems can also be built according to the invention.
• the dynamic balance of a vehicle is all the more important for the safety that the speed of movement of the vehicle is high. It should be noted that, when traveling at sustained speeds, the steering angles of the wheels are always quite low. If there is a blockage of a wheel in the slightly steered position, when returning to a straight line controlled by a steering wheel angle of zero, the principle proposed by the invention makes the vehicle will move crab in degraded mode, that is to say at a non-zero angle between the longitudinal axis of the vehicle and the direction of movement of the vehicle. This is quite acceptable because said angle is quite small. This angle could take important values if the failure of an actuator occurs at a low speed; this will result in a characteristic angle of a larger crab trajectory, which may not be very pleasant but not at all dangerous given the low speed at which this type of degraded mode will occur.
• the steering control system comprises at least a second management strategy in degraded mode based on a positioning of the CIR function of the 1 èr6 unblocked wheel which will arrive in mechanical stop.
• FIG. 1 is a layout diagram of an electrical steering system according to the invention. • Figure 2 shows a vehicle with four wheels all steering, in a steering configuration to the right during which occurs a locking of the right front wheel actuator;
• Figure 3 shows the situation of the vehicle operating in degraded mode allowing the vehicle to drive in a straight line
• Figure 4 shows the situation of the vehicle operating in degraded mode allowing the vehicle to turn left
• Figure 5 shows the degraded mode strategies for a four-wheeled vehicle all steering, in a steering configuration to the right during which occurs a locking of the right front wheel actuator.
• FIG. 1 there is a schematic four-wheeled vehicle 1 all directions.
• the steering wheels are mounted on a wheel carrier (not visible) and point about a pivot axis 10.
• a steering control lever 11 is mounted integral with the wheel carrier.
• Each steering wheel is pointed by an electric actuator 3 connected on the one hand to the body or chassis of the vehicle and on the other hand to the lever 11, to control the steering angle of the wheel in question.
• Each electric actuator 3 comprises for example a screw / nut device (not shown), actuated by a rotary electric motor.
• the screw of the screw / nut device is connected to the steering control lever 11.
• Each actuator preferably comprises a position sensor for, if necessary by geometric construction and associated calculations, to know from the measurement delivered by the position sensor the exact angular position of the steering wheel considered.
• ⁇ denotes any particular value (in amplitude and in sign) characterizing the command that the driver imposes on a control member to act on the direction of the vehicle; for example, it is a steering wheel that is maneuvered over a predetermined angular range (the concept of angle is not limiting in that the steering wheel can be substituted for any equivalent device such as a joystick or a cursor).
• the system comprises means 5 for detecting a locking of a steering wheel actuators capable of delivering, in the event of a detected blocking, an alert signal identifying the locked actuator.
• FIGS 2 to 4 show an illustration of the first strategy for calculating the steering angles of the unrestrained actuators of the degraded mode proposed by the present invention.
• the degraded mode calculates the angle of steering of the steering ⁇ pi unblocked wheels INB, that is to say the angles ⁇ pAvG, o ⁇ ArD, ⁇ PATG-
• the instantaneous center of rotation CIR of the vehicle must be maintained substantially on the straight line perpendicular to the plane of the right front wheel I AVD , the wheel locked, and passing through the center of the ground contact area of said front right wheel I AVD -
• the exact position of the CIR on said perpendicular line is function the requested steering angle ⁇ , which corresponds to a steering radius R desired by the driver. Note that the calculation of this radius is not part of the present invention, which is compatible with multiple ways of determining the radius R.
• the driver decreases the required steering angle ⁇ , ie wants to increase the turning radius R, the CIR will move from the right side to the right represented in centerlines, that is to say, it will move away from the vehicle. If the driver wishes to bring the vehicle back in a straight line, the configuration shown in Figure 3 is obtained. The radius R then tends towards infinity, the steering angle of the unobstructed wheel actuators I NB is identical on all the wheels and is equal to the angle of the actuator of the locked wheel. I AVD - The CIR is pushed back to infinity, which allows rolling in a straight line. The vehicle, operating in degraded mode, rolls in a straight line in an attitude called "crab".
• Figure 4 shows the situation of the vehicle operating in degraded mode from the blockage shown in Figure 2, if the driver now wants to turn his vehicle left.
• the locked wheel I AVD With respect to the locked wheel I AVD , the other unobstructed wheels I NB are pointed so as to position the CIR still on the right shown in phantom, perpendicular to the locked wheel 1 AVD , on the left side relative to the vehicle .
• the invention thus proposes a first degraded mode strategy that makes it possible to steer all the steering wheels around the same instantaneous center of rotation.
• the invention proposes a second and a third degraded mode strategies by which it is generally possible, ie in most situations encountered in practice, to print a yaw movement in the direction desired by the driver. .
• This can cause some shifting of the wheels on the ground, shifting quite acceptable during a maneuver normally short enough to maintain, despite a failure, the ability to control the path of the vehicle.
• FIG. 5 schematizes the degraded mode strategies for a four-wheeled vehicle all steering, in a steering configuration to the right during which there is a blockage of the vehicle. front right wheel actuator.
• said steering steering unit imposes a second degraded mode strategy by which the location of the instantaneous center of rotation CIR of the vehicle is bounded by the line B1 perpendicular to the plane of the wheel in abutment passing through the center of the ground contact area of said wheel abutment, right rear wheel here, and is located in the half plane ⁇ l towards the front of the vehicle relative to said terminal Bl, and the side towards infinity with respect to a straight line d2 parallel to the longitudinal axis of the vehicle passing through the instantaneous center of rotation CIR b1 effective when said steering stop has been reached.
• the instantaneous center of rotation CIR of the second degraded mode strategy is on a straight line D parallel to the direction transverse to the vehicle, passing through the instantaneous center of rotation CIR b1 effective at the moment when said steering stop has been reached.
• the CIR moves on the right D; the ARD wheel is no longer in abutment.
• This second degraded mode strategy makes it possible to gradually increase the turning radius R in order to satisfy the driver's steering demand, while limiting as much as possible the shifting of the wheels on the ground.
• the driver will therefore want to gradually decrease the turning radius R.
• the application of the first degraded mode strategy travels the CIR on the right “d” in a direction that tends to bring it closer to the vehicle to the CIR position b 2 , which is the instantaneous center of rotation (CIR b2 ) effective at the moment when the other steering stop was reached by the wheel ARD.
• CIR b2 instantaneous center of rotation
• said steering control unit imposes a third degraded mode strategy by which the location of the instantaneous center of rotation CIR of the vehicle is bounded by the line (B2) perpendicular to the plane of the wheel in abutment, right rear wheel here, passing by the center of the ground contact area of said wheel in abutment, the location of the instantaneous center of rotation CIR being on the one hand located in the half plane ⁇ 2 extending towards the rear of the vehicle relative to said terminal, and secondly on the vehicle side with respect to a straight line d3 parallel to the longitudinal axis of the vehicle and passing through the center instantaneous rotation CIR b2 effective when said other steering stop has been reached.
• the instantaneous center of rotation CIR of the third degraded mode strategy is on the straight line B2 perpendicular to the plane of the stop wheel passing through the center of the ground contact area of said wheel in abutment.
• the accidental locking of a wheel actuator is a phenomenon close to the case of an actuator in abutment. Therefore, the invention can also find application in the case where, although one of the actuators is in abutment, we want to further reduce the turning radius of the vehicle, of course by accepting that the wheels begin to rip.
• the third degraded mode strategy can then be applied, considering that the locked actuator and the actuator in abutment are one and the same actuator.
• the invention has been illustrated by applications to a four-wheeled vehicle, all guidelines. This is however not limiting.
• the vehicle may have any number of wheels, and not necessarily all of them. For example, take the case of an 8-wheel vehicle all steering.
• the management of the vehicle's CIR in normal mode makes it possible to calculate a steering angle for each of the eight wheels. Imagine that one of the eight wheels is stuck. We then hold the CIR on the line perpendicular to the plane of the locked wheel and we pilot the steering angle of the other 7 wheels so that they all turn around this CIR.
• the 2 nd and 3 rd control strategies in degraded mode, accepting a shifting of the wheels, are based on a positioning of the CIR based on the 1 Er6 not locked wheel will happen in mechanical stop. It does not matter if there are 3 or 7. The principle remains the same.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Mathematical Physics (AREA)
• Theoretical Computer Science (AREA)
• Steering Control In Accordance With Driving Conditions (AREA)
• Electric Propulsion And Braking For Vehicles (AREA)
• Vehicle Body Suspensions (AREA)
• Steering-Linkage Mechanisms And Four-Wheel Steering (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (1)

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ID=36010894

Family Applications (1)

Country Status (9)

Cited By (2)

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Citations (4)

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• 2005
  • 2005-07-04 FR FR0507178A patent/FR2887839B1/fr not_active Expired - Fee Related
• 2006
  • 2006-06-30 US US11/988,357 patent/US7912606B2/en not_active Expired - Fee Related
  • 2006-06-30 EP EP06778037A patent/EP1904359B1/fr not_active Not-in-force
  • 2006-06-30 JP JP2008518873A patent/JP5224590B2/ja not_active Expired - Fee Related
  • 2006-06-30 AT AT06778037T patent/ATE480437T1/de not_active IP Right Cessation
  • 2006-06-30 KR KR1020087002721A patent/KR101225276B1/ko not_active Expired - Fee Related
  • 2006-06-30 CN CN2006800243488A patent/CN101213127B/zh not_active Expired - Fee Related
  • 2006-06-30 WO PCT/EP2006/064758 patent/WO2007003661A1/fr not_active Ceased
  • 2006-06-30 DE DE602006016801T patent/DE602006016801D1/de active Active

Patent Citations (4)

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