WO2017072732A1 - Système de commande de direction assistée - Google Patents

Système de commande de direction assistée Download PDF

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Publication number
WO2017072732A1
WO2017072732A1 PCT/IB2016/056534 IB2016056534W WO2017072732A1 WO 2017072732 A1 WO2017072732 A1 WO 2017072732A1 IB 2016056534 W IB2016056534 W IB 2016056534W WO 2017072732 A1 WO2017072732 A1 WO 2017072732A1
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WO
WIPO (PCT)
Prior art keywords
vehicle
steering
stability
control unit
power steering
Prior art date
Application number
PCT/IB2016/056534
Other languages
English (en)
Inventor
Christian Nolin
Original Assignee
Bombardier Recreational Products Inc.
Brp Us Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bombardier Recreational Products Inc., Brp Us Inc. filed Critical Bombardier Recreational Products Inc.
Publication of WO2017072732A1 publication Critical patent/WO2017072732A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D61/00—Motor vehicles or trailers, characterised by the arrangement or number of wheels, not otherwise provided for, e.g. four wheels in diamond pattern
    • B62D61/06—Motor vehicles or trailers, characterised by the arrangement or number of wheels, not otherwise provided for, e.g. four wheels in diamond pattern with only three wheels
    • B62D61/065—Motor vehicles or trailers, characterised by the arrangement or number of wheels, not otherwise provided for, e.g. four wheels in diamond pattern with only three wheels with single rear wheel

Definitions

  • the present technology relates to power steering control systems.
  • Many vehicles are provided with a power steering system.
  • a power steering system when the driver applies steering torque to steer the vehicle, via a steering wheel or a handlebar for example, an actuator applies additional steering torque.
  • steering can be achieved with less effort from the driver compared with the effort required to steer the same vehicle without a power steering system.
  • the level of steering assistance provided by the power steering system could be constant, most power steering systems are provided with a control system that modulates the level of steering assistance based on various operating conditions of the vehicle.
  • Many power steering control systems reduce the level of steering assistance as the speed of the vehicle increases to take into account the reduction of steering resistance at the wheel and the greater inertial effect that a change in direction will have as the vehicle speed increases.
  • Many power steering control systems also increase the level of steering assistance as the amount of steering torque applied by the driver increases.
  • Other power steering systems also vary the level of steering assistance based on the steering angle as the geometry of the steering system can have an effect on the steering resistance. In such a system, the level of variation of steering assistance is typically controlled in order to provide a more linear steering feel to the driver as the steering angle changes.
  • Many power steering systems use a combination of two or more of the above operating conditions of the vehicle to control the level of steering assistance.
  • VSS vehicle stability systems
  • ESS electronic stability systems
  • ESP electronic stability program
  • ESC electronic stability control
  • Such systems typically include an onboard computer processor and associated memory that have programming to manage various vehicle systems to a degree to which a human driver of the vehicle cannot.
  • VSS can intervene by selectively applying a braking force at one or more wheels and/or slowing the engine in response to prevent, inter alia, locking of the brakes, a loss of traction or wheel lift.
  • Such interventions are initiated in response to information received from sensors such as a longitudinal acceleration sensor, a lateral acceleration sensor, a yaw rate sensor, an engine speed sensor, steering angle sensor or a wheel speed sensors. Examples of such a VSS are described in United States Patent Nos. 8,086,382, 8,655,565 and 9,043,111, the entirety of which are incorporated herein by reference.
  • a power steering system for a vehicle having a steering input device, a steering input device sensor sensing at least one of a steering angle of the steering input device and an input steering torque applied to the steering input device, a vehicle stability sensor for sensing an operating condition of the vehicle indicative of a stability of the vehicle, and at least one control unit electronically connected to the steering input device sensor and the vehicle stability sensor.
  • the steering input device sensor sends a signal representative of the at least one of the steering angle of the steering input device and the input steering torque applied to the steering input device to the at least one control unit.
  • the vehicle stability sensor sends a signal representative of the operating condition of the vehicle indicative of the stability of the vehicle to the at least one control unit.
  • a power steering actuator is electronically connected to the at least one control unit.
  • the power steering actuator is adapted for being operatively connected to at least one steerable ground engaging member of the vehicle.
  • the at least one control unit controls an operation of the power steering actuator based at least in part on the signal received from the steering input device and the signal received from the vehicle stability sensor.
  • a steering column operatively connects the steering input device to the power steering actuator.
  • the at least one ground engaging member of the vehicle is a pair of ground engaging members of the vehicle.
  • a pair of connecting rods is operatively connected to the power steering actuator and is adapted for operatively connecting the power steering actuator to the pair of steerable ground engaging members of the vehicle.
  • a vehicle speed sensor for sensing a vehicle speed is electronically connected to the at least one control unit and sends a signal representative of the vehicle speed to the at least one control unit.
  • the at least one control unit further controls the operation of the power steering actuator based on the signal received from the vehicle speed sensor.
  • the at least one control unit controls the operation of the power steering actuator to decrease an amount of steering assist provided by the power steering actuator as the stability of the vehicle decreases.
  • the at least one control unit controls the operation of the power steering actuator to decrease an amount of steering assist provided by the power steering actuator as the stability of the vehicle approaches a predetermined minimum stability of the vehicle.
  • the at least one control unit includes a variable stability system (VSS) control unit and a dynamic power steering (DPS) control unit.
  • the VSS control unit is electronically connected to the vehicle stability sensor.
  • the VSS control unit determines the stability of the vehicle based at least on the signal received from the vehicle stability sensor.
  • the DPS control unit is electronically connected to the power steering actuator to control the operation of the power steering actuator.
  • the VSS control unit sends a stability signal representative of the stability of the vehicle to the DPS control unit.
  • the DPS control unit controls the operation of the power steering actuator based at least in part on the stability signal.
  • the VSS control unit is adapted to control operation of brakes of the vehicle independently of a driver's braking input.
  • the VSS control unit determines braking torques to be applied to wheels of the vehicle based at least in part on the signal received from the vehicle stability sensor.
  • the stability signal includes data representative of the braking torques.
  • the VSS control unit determines at least one of a wheel lift condition and a wheel slip condition based at least in part on the signal received from the vehicle stability sensor.
  • the VSS control unit determines the stability of the vehicle based at least in part on a proximity between current operating conditions of the vehicle and the at least one of the wheel lift condition and the wheel slip condition.
  • the vehicle stability sensor is at least one of a longitudinal acceleration sensor, a lateral acceleration sensor and a yaw rate sensor.
  • the steering input device sensor is a steering angle sensor sensing the steering angle of the steering input device.
  • a steering torque sensor senses the input steering torque applied to the steering input device.
  • the steering torque sensor sends a signal representative of the input steering torque applied to the steering input device to the at least one control unit.
  • the at least one control unit further controls the operation of the power steering actuator based on the signal received from the steering torque sensor.
  • a vehicle having a frame, at least three ground engaging members operatively connected to the frame, at least two of the at least three ground engaging members being steerable ground engaging members, a motor supported by the frame and being operatively connected to at least one of the at least three ground engaging members for powering the at least one of the at least three ground engaging members, and the power steering system according to the aspect of the present technology described above and optionally according to one or more of the above implementations.
  • the power steering actuator is operatively connected to the at least two steerable ground engaging members.
  • the at least three ground engaging members are two steerable front wheels and a single rear wheel.
  • the motor is operatively connected to the single rear wheel.
  • the power steering actuator is operatively connected to the two steerable front wheels.
  • a straddle seat is supported by the frame.
  • the steering input device is a handlebar.
  • a method for controlling a power steering actuator of a power steering system for a vehicle comprising: determining an input steering torque applied to a steering input device of the vehicle; determining an assist level to be provided by the power steering actuator based on the input steering torque applied to the steering input device; determining a stability of the vehicle; determining a stability assist factor based on the stability; adjusting the assist level based on the stability assist factor; determining an output steering torque to be applied by the power steering actuator to steerable ground engaging members of the vehicle based on the input steering torque applied to the steering input device and the adjusted stability assist level; and causing the power steering actuator to apply the output steering torque to the steerable ground engaging members.
  • the method further comprises determining a vehicle speed.
  • the assist level and the stability assist factor are also determined based on the vehicle speed.
  • the method further comprises determining a steering angle of the steering input device; and determining a steering angle assist factor based at least in part on the steering angle.
  • the adjusted assist level is further based on the steering angle assist factor.
  • the assist level decreases as the stability decreases.
  • the method further comprises determining at least one of a wheel lift condition and a wheel slip condition.
  • the stability of the vehicle is determined based at least in part on a proximity between current operating conditions of the vehicle and at least one of a wheel lift condition and a wheel slip condition.
  • the stability of vehicle is determined based at least in part at least one signal received from at least one of a longitudinal acceleration sensor, a lateral acceleration sensor and a yaw rate sensor.
  • Implementations of the present technology each have at least one of the above- mentioned object and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein.
  • Figure 1 is a right side elevation view of a three- wheel vehicle
  • Figure 2 is a perspective view taken from a front, right side of a steering system of the vehicle of Fig. 1 ;
  • Figure 3 is a perspective view taken from a rear, right side of the steering system of Fig. 2;
  • Figure 4 is an exploded view of the steering system of Fig. 2;
  • Figure 5 is a schematic illustration of various components of the vehicle of Fig. 1 ;
  • Figure 6 is a graph illustrating an assist level of a power steering system of the vehicle of Fig. 1 with respect to vehicle speed and user torque used by a power steering control system of the vehicle of Fig. 1 ;
  • Figure 7 is a graph illustrating a steering angle assist factor with respect to vehicle speed and absolute steering angle used by the power steering control system
  • Figure 8 is a graph illustrating the tire grip threshold and vehicle wheel lift threshold of a typical rear wheel drive three-wheel vehicle having two wheels in the front and one wheel in the rear;
  • Figure 9 is a graph illustrating a stability assist factor with respect to vehicle speed and stability used by the power steering control system.
  • Figure 10 is a logic diagram illustrating a manner in which steering torque output is determined.
  • the present technology will be described with respect to a three-wheel vehicle having two front wheels, a single rear wheel and a straddle seat. However, it is contemplated that at least some aspects of the present technology could be used on other types of vehicles having a power steering system, such as, but not limited to, all-terrain vehicles (ATVs), side- by-side off-road vehicles and automobiles. It is also contemplated that at least some aspects of the present technology could be used on vehicles having one or more ground engaging member that is not a wheel such as, but not limited to, an endless drive track.
  • ATVs all-terrain vehicles
  • ground engaging member that is not a wheel such as, but not limited to, an endless drive track.
  • Fig. 1 illustrates a three-wheel vehicle 10 having a straddle seat 12 adapted to accommodate one or two adult sized riders.
  • the straddle seat 12 includes a forward seat portion 14 for the driver and a rear seat portion 1 6 for a passenger.
  • the rear seat portion 16 is removable from the vehicle 10. It is contemplated that the forward seat portion 14 could also be removable from the vehicle 10. It is also contemplated that the forward and rear seat portions 14, 16 could be integrally formed and that such a unitary seat could be removable or not from the vehicle 10.
  • a handle 18 is provided beside each side of the rear seat portion 16.
  • a pair of foot pegs 20 (one foot peg 20 on each side of the three- wheel vehicle 10) and a pair of foot pegs 22 (one foot peg 22 on each side of the three- wheel vehicle 10) are used by the driver and the passenger respectively, for resting their feet onto during riding.
  • a brake pedal 24 for braking the vehicle 10 is provided above the right foot peg 20.
  • the three-wheel vehicle 10 has a frame 26.
  • the straddle seat 12 is mounted to and supported by the frame 26.
  • a motor 28 (schematically shown in Fig. 1) is mounted to and supported by the frame 24 forward of the straddle seat 12.
  • the motor 28 is an internal combustion engine, but any type of power source is contemplated such as, but not limited to, an electric motor.
  • Body panels 30 are connected to the frame 26. At the front of the vehicle 10, the body panels 30 at least partially enclose the motor 28. One of the body panels 30 forms a hood 32 mat can be pivoted to access a front storage bo (not shown).
  • the body panels 30 also define apertures or recesses to receive the headlights 34 (only one of which can be seen in Fig. 1) of the vehicle 10.
  • Rearview mirrors 36 (only one of which can be seen in Fig. 1) are mounted to the body panels 30 forward of the seat 12.
  • Two storage container assemblies 38 are mounted to the frame 24 at a rear of the three-wheel vehicle 10 (one on each side) behind the pair of foot pegs 24. As can be seen for the right storage container assembly 38, the storage container assemblies 38 are disposed beside the seat portion 16 on either side thereof below the handles 18. It is contemplated that only one storage container assembly 38 could be provided or that they could be omitted.
  • a single rear wheel 40 is mounted to a swing arm 42, which forms part of the frame 26, and is suspended from the vehicle 10 via a rear suspension system 44 at the rear of the frame 26.
  • the single rear wheel 40 is driven by the motor 28 via a belt and sprocket system and a transmission (not shown).
  • a rear fender 46 partially covers the rear wheel 40.
  • a pair of front wheels 48 (only the front right wheel being shown in Fig. 1) is suspended from the front of the frame 26 via front suspension assemblies (not shown).
  • the front wheels 48 are operatively connected to a steering system 50 that includes a handlebar 52. When the driver turns the handlebar 52 in one direction, the front wheels 48 are steered in the corresponding direction.
  • a throttle actuator 54 for controlling the speed of the vehicle 10 is provided on the handlebar 52.
  • the steering system 50 includes a handlebar 52. It is contemplated that the handlebar 52 could be replaced by another type of steering input device depending on the type of vehicle or driver preference.
  • the steering input device is a steering wheel.
  • Other types of steering input device include, but are not limited to, a joystick, a tiller and yoke.
  • the handlebar 52 has a central generally U-shaped portion 56 (not shown in Fig. 4) and left and right straight rods 58.
  • the rods 58 are fastened to the ends of the central portion 56.
  • Handle grips 60 (Fig. 4) are disposed over the straight rods 58.
  • Caps 62 are fastened to the ends of the straight rods 58 to prevent the handle grips 60 from, sliding off the rods 58.
  • the central portion 56 of the handlebar 52 is connected to the upper end of an upper steering column 64 (Fig. 4) by a clamp 66 (Figs. 2 and 3).
  • the upper steering column 64 is received in a steering column support 68.
  • Cushions 70 are provided between the upper steering column 64 and the steering column support 68 such that the upper steering column 64 can rotate inside the steering column support 68.
  • the steering column support 68 is fastened to the frame 26 of the vehicle 10.
  • the lower end of the upper steering column 64 is splined.
  • the splined end of the upper steering column 64 is inserted inside an upper portion of an upper universal joint 72 having internal splines.
  • a fastener 74 inserted through the upper portion of the upper universal joint 72 passes inside a groove 76 in the lower end of the upper steering column 64 to hold the upper steering column 64 and the upper universal joint 72 together.
  • a flexible boot 78 is connected to the steering column support 68 and covers the universal joint 72.
  • the lower portion of the universal joint 72 is fixedly connected to a lower steering column 80.
  • the lower steering column 80 is divided into an upper portion 80A and a lower portion 80B that are connected by a collar 82 at the lower end of the upper portion 80A.
  • the collar 82 defines internal splines and the lower portion 80B has a correspondingly splined input end 84 (Fig. 4).
  • the upper portion 80A extends between the universal joint 72 and a power steering actuator 86.
  • the lower portion SOB extends through the power steering actuator 86.
  • the input end 84 extends above the power steering actuator 86 and an output end 92 extends below the power steering actuator 86.
  • the power steering actuator 86 has an electrical motor 88 operatively connected to a gearbox 90 to drive the gearbox 90.
  • the lower portion SOB is also operatively connected to the gearbox 90 to drive the gearbox 90 via splines (not shown) that extend around a circumference thereof.
  • the driver of the vehicle 10 exerts a force on the handlebar 52 which is transmitted through the upper and lower steering columns 64 and 80, and on to the wheels as will be described in further detail below.
  • the electrical motor 88 applies a torque to the lower portion SOB via the gearbox 90 to assist in steering the front wheels 48.
  • the output steering torque of the power steering actuator 86 is greater man the steering torque input by the driver.
  • the gearbox 90 is fastened to the frame 26 of the vehicle 10.
  • a steering sensor angle sensor 180 (Fig. 5) is mounted to a sensor support 94 which is connected to the bottom of the gearbox 90.
  • a steering torque sensor 182 (Fig. 5), which detects the steering torque applied by the driver, is mounted within the power steering actuator 86.
  • the power steering actuator 86 is electrical.
  • Other types of power steering actuators are contemplated, such as, but not limited to, a hydraulic steering actuator including a hydraulic pump. The method for controlling the power steering actuator 86 will be described in greater detail below.
  • a pitman arm 96 is connected to the output end 92 of the lower portion SOB and pivots with the output end 92.
  • the pitman arm 96 provides two connection points to which left and right tie rods 98 are connected.
  • the tie rods 98 are pivotally connected to the pitman arm 96 by ball joints 100.
  • the distal ends of the tie rods 98 are pivotally connected to left and right steering knuckles 102 via ball joints 104.
  • the steering knuckles 102 receive the axles (not shown) of the front wheels 48 therein.
  • the upper and lower steering columns 64, 80 turn with it in the same direction and apply an input steering torque to the input shaft 84 of the power steering actuator 86.
  • the power steering actuator 86 then provides a certain level of steering assistance as will be described in greater detail below, and the power steering steering actuator 86 applies an output steering torque to the output end 92.
  • the pitman arm 96 turns in the same direction as the handlebar 52.
  • the pitman arm 96 pushes/pulls (as the case may be) on the tie rods 98, which then cause the steering knuckles 102 to turn about their respective steering axes 106.
  • the front wheels 48 are steered in the same direction as the handlebar 52.
  • the vehicle 10 has an engine control module (ECM) 150, made of multiple control units, which electronically communicates with a vehicle stability system (VSS) control unit 152.
  • the ECM 150 and the VSS control unit 152 electronically communicate with a dynamic power steering (DPS) control unit 154.
  • the VSS control unit 152 includes a computer processor and processor readable memory containing both programming information (software) and data respecting the VSS's functions.
  • the ECM 150 controls the operation of the engine 28 as described below.
  • the VSS control unit 152 controls the operation of a vehicle stability system that, as the name suggest, helps control the stability of the vehicle 10 as described below.
  • the DPS control unit 154 controls the operation of the power steering actuator 86 as will, be described below.
  • the architecture of the control units illustrated in Fig. 5 is only one example of a contemplated implementation of architecture of the control units. It is contemplated that certain functions of the various control units could be carried out by a control unit other than the one described below. It is contemplated that the functions of two or more of the control units described herein could be combined in a common control unit. It is also contemplated that the functions of a control unit described herein could be split into multiple control units. It is also contemplated that the control units described herein could communicate with each other differently than as described herein. For example, it is contemplated that the ECM 150 and the DPS control unit 154 could communicate directly with each other.
  • the vehicle 10 has multiple sensors, some of which are described below. It is contemplated that the vehicle 10 could have more sensors than the ones described below and that one or more of the sensors described below could be omitted. It is also contemplated that the sensors illustrated in Fig. 5 could be electronically connected to one or more of the control units 150, 152, 154 other than the one or more control units 150, 152, 154 they are described as being electronically connected to below.
  • a throttle actuator position sensor 156 senses a position of the throttle actuator 54 and sends a signal indicative of this position to the ECM 150.
  • the throttle actuator position sensor 156 is the only sensor being shown as being directly connected to the ECM 150, it is contemplated that other sensors could be connected directly to the ECM 150.
  • one or more of an air pressure sensor, an air temperature sensor, a throttle valve position sensor and an engine speed sensor could be provided and connected directly to the ECM 150.
  • the ECM 150 uses the signal from the throttle actuator position sensor 156, signals received from the VSS control unit 152 and from other sensors to control the operation of the engine 28.
  • the ECM 150 sends control signals to the fuel injectors 158, the throttle valve actuator 160 and spark plugs 162 of the engine 28 in order to control operating parameters of the engine 28 such as engine speed and engine torque.
  • a front left wheel speed sensor 164 senses a speed of rotation of the front left wheel 48.
  • a front right wheel speed sensor 166 senses a speed of rotation of the front right wheel 48.
  • a rear wheel speed sensor 168 senses a speed of rotation of the rear wheel 40.
  • the wheel speed sensors 164, 166, 168 are electronically connected to the VSS control unit 152 and send signals representative of the speed of rotation of their respective wheels 40, 48 to the VSS control unit 152.
  • the VSS control unit 152 uses the signals from the wheel speed sensors 164, 166, 168 and the steering angle, obtained from the steering angle sensor 180 (described below), to calculate the vehicle speed of the vehicle 10. It is contemplated that only one or two of the wheel speed sensors 164, 166, 168 could be used to determine the vehicle speed. It is also contemplated that the wheel speed sensors 164, 166 and 168 could be used to determine wheel slip. It is also contemplated that if only the rear wheel speed sensor 168 is used, the steering angle could be ignored in the determination of the vehicle speed.
  • An optional rear wheel sensor 170 may be provided for implementations adapted for a four-wheel vehicle, in which case the rear wheel sensor 168 would sense the speed of rotation of one of the rear wheels and the rear wheel sensor 170 would sense the speed of rotation of the other one of the rear wheels.
  • the wheel speed sensor 170 sends a signal representative of the speed of rotation of its associated wheel to the VSS control unit 152 that uses this additional signal to determine the vehicle speed.
  • the VSS control unit 152 sends a signal representative of the vehicle speed to the ECM 150 that uses it to control the engine 28 and to the DPS control unit 154 that uses it to control the power steering actuator 86.
  • Other types of sensors could be used to determine the vehicle speed, such as, but not limited to, a global positioning system.
  • the VSS control unit 152 also compares the speeds of rotation of the wheels 40, 48 to determine a stability of the vehicle 10.
  • a passenger presence sensor 172 is provided under the rear seat portion 16.
  • the passenger presence sensor 172 is electronically connected to the VSS control unit 152 and sends a signal indicative of the presence (or absence) of a passenger on the rear seat portion 16 to the VSS control unit 152.
  • the presence of a passenger in addition to causing a difference in the overall weight, the presence of a passenger also changes the position of the center of gravity of the vehicle 10.
  • the VSS control unit 152 also uses this signal to adjust the manner in which the stability of the vehicle is controlled. Similar sensors could be used to determine the presence or absence of cargo in the cargo boxes 38 for similar reasons.
  • the VSS control unit 152 also transmits signals to the ECM 150 as a function of the presence or absence of the passenger, which then uses this information to adjust the control of the engine 28. It is contemplated that the passenger presence sensor 172 could be omitted. Additional detail and information regarding implementations of a passenger presence sensor, such as the passenger presence sensor 172, can be found in United States Patent No. 8,260,535, issued September 4, 2012, the entirety of which is incorporated herein by reference. [0062]
  • the vehicle 10 also has three vehicle stability sensors: a longitudinal acceleration sensor 174, a lateral acceleration sensor 176 and a yaw rate sensor 178. It is contemplated that the vehicle 10 could have more or less than three vehicle stability sensors and that other types of vehicle stability sensors could be used.
  • a roll rate sensor could be provided instead of one of the above three vehicle stability sensors or in addition to the above three vehicle stability sensors.
  • the longitudinal acceleration sensor 174 senses a longitudinal acceleration of the vehicle 10.
  • the lateral acceleration sensor 176 senses a lateral acceleration of the vehicle 10.
  • the yaw rate sensor 178 senses a yaw rate of the vehicle.
  • the vehicle stability sensors 174, 176, 178 are electronically connected to the VSS control unit 152 and send signals representative of the vehicle operating conditions that they measure to the VSS control unit 152.
  • the VSS control unit 152 uses the signals from the vehicle stability sensors 174, 176, 178, the steering angle, obtained from the steering angle sensor 180 (described below), and the wheel speed sensors 164, 166, 168 to determine the stability of the vehicle 10 and to control the stability of the vehicle 10 as will be described below.
  • the VSS control unit 152 sends a signal to the ECM 150 that uses it to control the engine 28 and a signal to the DPS control unit 154 that uses it to control the power steering actuator 86 as will be described below.
  • the steering angle sensor 180 is connected to the sensor support 94 to sense an angular position of the output end 92 of the lower portion 80B of the lower steering column 80.
  • the angular position of the output end 92 corresponds to the angular position of the steering columns 64, 80 resulting from the angular position of the handlebar 52 in response to the steering input of the driver of the vehicle 10.
  • the steering angle sensor 180 senses the steering angle. It is contemplated, that the steering angle sensor 180 could be located elsewhere so as to sense the angular position of the handlebar 52, the steering column 64 or the steering column 80. It is contemplated that the angular position of the output end 92 may not correspond directly to the angular position of the steering columns 64, 80 and the handlebar 52, but that the corresponding angular positions of these elements could be determined from the gear ratio of the gearbox 90.
  • the steering angle sensor 180 is electronically connected to the VSS control unit 152 and the DPS control unit 154.
  • the steering angle sensor 180 sends signals indicative of the steering angle to the VSS control unit 152 and the DPS control unit 154. It is also contemplated that the steering angle could be determined by sensing the angular positions of the steering knuckles 102 or by sensing the lateral displacement of the tie rods.
  • the steering torque sensor 182 mounted along the lower portion 80B of the lower steering column 80, senses the input steering torque applied by the driver to the handlebar 52 when steering. It is contemplated that the steering torque sensor 182 could alternatively sense the input steering torque at the handlebar 52, at the upper steering column 64 or along the upper portion 80A of the lower steering column 80.
  • the steering torque sensor 182 is electronically connected to the DPS control unit 154 and sends a signal indicative of the input steering torque applied to the handlebar 52 to the DPS control unit 154. It is contemplated that the DPS control unit 154 could send a signal representative of the input steering torque to the VSS control unit 152. It is contemplated that a single sensor could be used to sense both the input steering torque and the steering angle.
  • the vehicle stability system provides, inter alia, rollover mitigation (ROM), anti-lock braking (ABS) and traction control (TC). It is contemplated that one or more of these functions could be provided in one or more separate systems, with each system having its own control unit. It is also contemplated that one or two of the functions of the vehicle stability system could be omitted and/or replaced by one or more functions and/or that the vehicle stability system could have additional functions.
  • ROM rollover mitigation
  • ABS anti-lock braking
  • TC traction control
  • the vehicle stability system is controlled by the VSS control unit 152 that determines the dynamic status of the vehicle 10 based on inputs received from the various sensors described above and evaluates whether the vehicle dynamic status falls within or outside the limits of a stability envelope of the vehicle 10 stored in memory and below or above a maximum rate of change of the vehicle dynamic status stored in memory. Should the VSS control unit 152 determine that the vehicle is at or near the limits of the stability envelope, such as, but not limited to, conditions related to understeer, oversteer, wheel lift and wheel lock, the VSS control unit 152 controls various components of the vehicle 10 to improve or restore stability.
  • the VSS control unit 152 sends signals to one or more of the actuators of the front left brake 184, the front right brake 186 and the rear brake 188 of the front left wheel 48, the front right wheel 48 and the rear wheel 40 respectively to cause one or more brakes 184, 186, 188 to apply more or less braking torque to one or more corresponding wheels 40, 48 independently of braking inputs from the driver.
  • the signals sent from the VSS control unit 152 to the brakes 184, 186 and/or 188 are hydraulic signals which control the force exerted by a hydraulic brake caliper (not shown) on a respective brake disc (not shown) at each wheel 40 and 48, although other braking mechanisms such as drum brakes are contemplated.
  • the VSS control unit 152 controls a hydraulic pump (not shown) and a set of valves (not shown) within a hydraulic manifold (not shown) that distribute hydraulic pressure generated by either the hydraulic pump or a brake master cylinder (not shown) actuated by the driver to the brakes 184, 186 and 188.
  • the signals sent by the VSS control unit 152 could be electric or electronic signals that control electromechanical brakes.
  • the VSS control unit 142 can, under certain conditions, send a signal to the ECM 150 such that the ECM 150 modifies the control of the engine 28 to reduce the engine speed/torque.
  • the VSS control unit 152 of the present technology sends a stability signal representative of the stability of the vehicle 10, or to the DPS control unit 154, which then uses this signal as indicated below to control the power steering actuator 86 in order to use the power steering actuator 86 to provide the driver with feedback related to the dynamic status of the vehicle and thereby help the driver stay within the limits of the stability envelope of the vehicle 10.
  • the stability signal includes data representative of the braking torques applied by the brakes 184, 186, 188.
  • a fourth brake 190 is provided that can also be controlled by the VSS control unit 152.
  • Figs. 6 to 10 a method used by the DPS control unit 154 to control the power steering actuator 86 will be described. The method will be described with respect to various graphs (Figs. 6, 7 and 9) to facilitate understanding. However, data corresponding to these graphs is stored as data maps in the DPS control unit 154 or in a separate data storage device that can be accessed by the DPS control unit 154. It is also contemplated that at least some of the maps could be omitted and replaced by mathematical formulas stored in and used by the DPS control unit 154 to calculate the corresponding output value. In addition, for clarity, the graphs of Figs. 6, 7 and 9 only illustrate data corresponding to three different vehicle speeds (0, 50 and 100 km/h).
  • the data maps stored in the DPS control unit 154 could include data for more than three vehicle speeds.
  • the data maps (and the graphs of Figs. 6, 7 and 9) include a discrete set of data point
  • the DPS control unit 154 uses interpolation techniques to determine the values corresponding to data points intermediate the data points present in the data maps.
  • the shape of the curves in the graphs of Figs. 6, 7 and 9 are provided to provide a general understanding of the relationship between the input and output data. It should be understood that the specific curves for a specific vehicle can be determined experimentally or through scientific modelling and that the curves will vary from one vehicle to another depending many factors. These factors may include, but are not limited to, vehicle dimensions, vehicle weight, position of the center of gravity of the vehicle, number of wheels, wheel size, tire type, powertrain, power steering actuator type, and steering system geometry.
  • the DPS control unit 154 determines an initial assist level X that forms the basis of the assist to be provided by the power steering actuator 86.
  • the initial assist level X corresponds to an amount of torque to be provided by the power steering actuator 86 based on the input steering torque and the vehicle speed.
  • the DPS control unit 154 uses the value of the input steering torque received from the steering torque sensor 182 and the value of the vehicle speed received from the VSS control unit 152. From these two values, the DPS control unit 154 can determine the initial assist level X. In the graph of Fig. 6, the initial assist level X is indicated as a percentage.
  • the percentage corresponds to a percentage of the maximum torque that can be applied by the power steering actuator 86 within its normal operating range.
  • the graph is modified such that the percentage on the vertical axis corresponds to a percentage of the input steering torque.
  • the percentage on the vertical axis could have a maximum value that is above or below 100 percent depending on the maximum torque that can be applied by the power steering actuator 86.
  • the graph is modified such that the vertical axis provides the value of the torque to be applied by the power steering actuator 86 directly.
  • the DPS control unit 154 also uses data received from the steering angle sensor 180 and/or the steering torque sensor 182 to determine in which direction the torque is to be applied by the power steering actuator 86.
  • the DPS control unit 154 also determines a steering angle assist factor Y.
  • the steering axes 106 of the vehicle 10, as in most vehicles, are not vertical.
  • the steering axes 106 have a camber angle, a caster angle and trail. These angles affect the handling characteristics of the vehicle 10. For example, a negative camber angle improves the grip of the tire of the outside tire with the road when turning and a positive caster angle provides a certain self-centering of the steering. Due to these angles, the contact patch (i.e. the area of contact between the tire and the road) can move and change in size as a wheel 48 is turned. Therefore, steering resistance varies over the range of angles of the steering system.
  • the steering angle assist factor Y is therefore used to account in the variations in steering resistance resulting from the steering system geometry and thereby can provide a more linear steering feel to the driver turning the handlebar 52.
  • the DPS control unit 154 uses the absolute value of the steering angle received from the steering angle sensor 180 and the value of the vehicle speed received from the VSS control unit 152 to determine the steering angle factor Y.
  • the steering angle ranges from 0 to 45 degrees as the output end 92 of the lower steering column 80 turns by a maximum of 45 degrees in each direction to achieve the full range of steering motion. It should be noted that the steering angle does not necessarily correspond to the angle of the wheels 48 with respect to a longitudinal centerline of the vehicle 10 due to the Ackermann steering geometry of the steering system.
  • the Ackermann steering geometry causes the wheel 48 on an inside of the turn to turn more than the wheel 48 on the outside of the turn because the inside wheel 48 needs to move along a circle having a smaller radius of curvature than the circle along which the outside wheel 48 needs to move and thereby reduces the effect of tire slip during a turn.
  • the graph of Fig. 7 could be modified such that the horizontal axis corresponds to the angle of the steering input device, which depending on the type of steering system, may or may not have a one to one correspondence to the angle of the output end 92 of the lower steering column 80. For example, in some vehicle having a steering wheel as the steering input device, more than one full rotation of the steering wheel in each direction may be necessary to move wheels through their full range of steering positions.
  • the DPS control unit 154 can determine the steering angle assist factor Y.
  • the steering angle assist factor Y is expressed as a positive real number from 0.0 to 1.0. It is contemplated that the steering angle assist factor Y could alternatively be expressed as a percentage.
  • the initial assist level X is adjusted by multiplying it by the steering angle assist factor Y. Therefore, as the steering angle assist factor Y decreases, so does the amount of steering assist provided by the power steering actuator 86.
  • the steering angle assist factor Y is constant at 1.0.
  • the steering assist factor Y decreases as the vehicle speed increases.
  • the steering assist factor Y initially increases up to a peak of 1.0 and then decreases.
  • the curve reaches its peak of 1.0 at a smaller steering angle and the pre- and post-peak minimum values for the steering angle assist factor Y are smaller.
  • the determination of the steering angle assist factor Y may be omitted such as, for example, in a vehicle where the steering axes axes are vertical (i.e. 0 degree of caster and 0 degree of camber) or may be modified to fit a given vehicle.
  • the DPS control unit 154 also determines a stability assist factor Z based in part on the stability of the vehicle.
  • the VSS control unit 152 continuously determines a measure of the stability of the vehicle 10 based on the signals it receives from the ECM 150 and the various sensors connected to the VSS control unit 152.
  • the VSS control unit 152 may modify the braking torque applied by one or more of the brakes 184, 186, 188 and may cause the ECM 150 to reduce the engine speed.
  • a high level of corrective activity of the VSS control unit 152 is indicative of a proximity to the limits of the stability envelope of the vehicle 10.
  • the VSS control unit 152 sends a signal corresponding to the vehicle stability to the DPS control unit 154. It is also contemplated that the VSS control unit 152 could send a signal or signals indicative of various stability -related parameters that can be used by the DPS control unit 154 to calculate an estimate of vehicle stability.
  • the stability of the vehicle 10 is expressed by a real number from 0.0 to 1.0, with 0.0 being the least stable and 1.0 being the most stable .
  • the vehicle 10 being at rest on level ground would have a stability of 1.0. It is contemplated that the stability could alternatively be expressed as a percentage.
  • the VSS control unit 152 starts reducing the stability value as soon as the vehicle 10 starts moving and the stability value decreases as stability decreases.
  • the VSS control unit 152 maintains the stability value at 1.0 within a certain range of operating conditions and then starts reducing the stability value once the operating conditions are outside this range and this value decreases as the operating conditions approach a minimum acceptable operating condition of the vehicle 10.
  • the stability of the vehicle 10 can be determined in many different ways.
  • stability can be determined by the VSS control unit 152 from the data obtained from one or more of the longitudinal acceleration sensor 174, the lateral acceleration sensor 176 and the yaw rate sensor 178. A high reading from any one of these can be indicative of proximity to the limits of the stability envelope and can therefore be converted to a corresponding stability value.
  • the VSS control unit 152 determines stability by comparing the data obtained from the front left and front right wheel speed sensors 164, 166, as a high difference between these two values can be indicative of proximity to the limits of the stability envelope and can therefore be converted to a corresponding stability value.
  • the VSS control unit 152 can also provide a stability value to the DPS control unit 154 by calculating a weighted average of the braking torques applied by the brakes 184, 186, 188 as a result of VSS intervention.
  • the average is weighted since the torque applied to the three wheels 40, 48 are not equally important. For example, since the rear wheel 40 is laterally centered, it does not carry as much weight as the front wheels.
  • the weighted average braking torque can be converted to a stability value, with increasing weighted average braking torques resulting in smaller stability values.
  • the VSS control unit 152 can provide braking torque data to the DPS control unit 154 and the DPS control unit 154 calculates a weighted average to determine a stability value.
  • the VSS control unit 152 can determine the dynamic status of the vehicle 10 by receiving data from a sensor (not shown) measuring a pressure applied to the shock absorber of the front wheels 48 or a degree of extension of the front shock absorbers (not shown) as a low pressure or a high degree of extension for one of the front wheels 48 can be indicative of a possible wheel lift, and therefore proximity to the limits of the stability envelope.
  • the VSS control unit 152 uses data received from the longitudinal and lateral acceleration sensors 174, 176 to determine how close to the wheel lift threshold (curve 200 in Fig. 8) and to the tire grip threshold (curve 202 in Fig. 8) the vehicle 10 is operating.
  • the manner in which the VSS control unit 152 controls the stability of a vehicle similar to the vehicle 10 is explained in detail in United States Patent No. 8,086,382. The closer the current longitudinal and lateral accelerations of the vehicle 10 are to the curves 200, 202, the smaller the stability value determined by the VSS control unit 152 gets. It is contemplated that the stability value could be determined to be 1.0 for all operating conditions below the curve 204 in Fig.
  • the stability value could start decreasing in the hatched region above the curve 204, with the stability value becoming smaller as the operating conditions get closer to the curve 200 or 202. It is also contemplated that the stability value could depend on which zone within the graph of Fig. 8 the current lateral and longitudinal accelerations are. In one example, below the curve 206 the stability is 1.0, between the curves 206 and 208 the stability is 0.8, between the curves 208 and 210 the stability is 0.6, between the curves 210 and 204 the stability is 0.4, and between the curve 204 and the curves 200, 202 the stability is 0.2. It is contemplated that two or more of the above implementations could be combined by the VSS control unit 152 to determine the stability of the vehicle 10.
  • the DPS control unit 154 uses the stability value and the value of the vehicle speed received from the VSS control unit 152 to determine the stability assist factor Z.
  • the stability assist factor Z is expressed as a positive real number from 0.0 to 1.0. It is contemplated that the stability assist factor Z could alternatively be expressed as a percentage.
  • the initial assist level X is adjusted by multiplying it by the stability assist factor Z. Therefore, as the stability assist factor Z decreases, so does the amount of steering assist provided by the power steering actuator 86.
  • the stability assist factor Z is initially 1.0 for all vehicle speeds when the stability value is 1.0. As stability decreases, the stability assist factor Z also decreases. Also, for stability values below 1.0, as vehicle speed increases, the stability assist factor Z decreases. Therefore, the less stable the vehicle 10 becomes, the less steering assist will be provided by the power steering actuator 86. By providing less steering assist under such conditions, steering becomes harder for the driver, thereby providing feedback to the driver that they are approaching the limits of the stability envelope and hindering their continued steering in a direction that could further decrease stability. As the vehicle speed increases, the steering assist is increasingly reduced to account for the reduction in steering resistance at the wheel as the vehicle speed increases and to account for the vehicle 10 becoming less stable faster and/or more easily at high speed. By hindering steering in a direction that would make the vehicle 10 less stable, VSS intervention could be reduced, thus improving ride quality for the driver and potentially increasing the life of the brakes 184, 186, 188.
  • the stability assist factor Z could have different values depending on whether the driver is trying to increase or decrease the steering angle as determined from a change in values obtained by from the steering angle sensor 180.
  • the stability assist factor Z when the driver is steering in a direction that would make the vehicle 10 less stable would be smaller than when the driver is steering in a direction that would make the vehicle 10 more stable.
  • the stability assist factor Z could be more than 1.0 to boost steering assist in a direction that would increase stability of the vehicle 10.
  • the DPS control unit 154 calculates an initial amount of assist steering torque from the input steering torque obtained from the steering torque sensor 182 and the initial assist level X determined as explained above. For example, for an input steering torque of 50 Nm and a vehicle speed of 50 km/h, the initial assist level X is determined to be 45 percent of the maximum torque that can be applied by the power steering actuator 86. Then at step 252, the DPS control unit 154 multiplies the result from step 250 by the the steering angle assist factor Y determined as explained above. Then at step 254, the DPS control unit 154 multiplies the result from step 252 by the the stability assist factor Z determined as explained above.
  • step 254 sets the amount of steering torque to be applied by the power steering actuator 86.
  • the DPS control unit 154 sends a signal to the electric motor 88 to control the operation of the electric motor 88 such that the power steering actuator 86 applies this amount of torque.
  • the sum (illustrated by the operator 256 in Fig. 10) of the torque applied by the driver (i.e. the input steering torque) and the torque applied by the power steering actuator 86 is the output steering torque applied to the lower steering column 80 which is the transmitted to the wheels 48.
  • the stability assist factor Z could be used in a steer-by-wire steering system.
  • the steering input device is not mechanically connected to the power steering actuator and to the wheels. There is no steering column linking the steering input device to the power steering actuator and the wheels. As such, all the steering torque is applied by the power steering actuator as the torque applied by the driver to the steering input device is not transmitted to the wheels.
  • the stability assist factor Z could be used to determine the output steering torque to be applied by the power steering actuator in order to take the vehicle stability into account. Should the steering input device be provided with a force feedback system, the stability assist factor Z could also be used to increase the resistance to steering applied by the force feedback system as vehicle stability decreases.

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

Abstract

La présente invention concerne un système de direction assistée pour un véhicule qui comporte un dispositif d'entrée de direction, un capteur de dispositif d'entrée de direction, un capteur de stabilité de véhicule pour détecter une condition de fonctionnement du véhicule indicative d'une stabilité du véhicule, et au moins une unité de commande électroniquement connectée au capteur de dispositif d'entrée de direction et au capteur de stabilité de véhicule. Le capteur de dispositif d'entrée de direction envoie un signal représentatif d'au moins l'un parmi un angle de direction et un couple de direction d'entrée à l'au moins une unité de commande. Le capteur de stabilité de véhicule envoie un signal représentatif de la condition de fonctionnement de l'au moins une unité de commande. Un actionneur de direction assistée est électroniquement connecté à l'au moins une unité de commande. L'au moins une unité de commande commande un fonctionnement de l'actionneur de direction assistée sur la base, au moins en partie, des signaux reçus. L'invention concerne en outre un véhicule comportant le système de direction assistée.
PCT/IB2016/056534 2015-10-30 2016-10-28 Système de commande de direction assistée WO2017072732A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201562248777P 2015-10-30 2015-10-30
US62/248,777 2015-10-30

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11014607B2 (en) 2018-05-31 2021-05-25 Bombardier Recreational Products Inc. Steering system for a vehicle

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030102180A1 (en) * 2001-12-05 2003-06-05 Badenoch Scott Wilson Adaptive variable effort power steering system
US20060064213A1 (en) * 2001-11-21 2006-03-23 Jianbo Lu Enhanced system for yaw stability control system to include roll stability control function
US20070045020A1 (en) * 2005-09-01 2007-03-01 Martino Marc G Three-wheeled vehicle with centrally positioned motor and driver's seat
US20100228417A1 (en) * 2009-03-06 2010-09-09 Gm Global Technology Operations, Inc. Driver hands on/off detection during automated lane centering/changing maneuver

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060064213A1 (en) * 2001-11-21 2006-03-23 Jianbo Lu Enhanced system for yaw stability control system to include roll stability control function
US20030102180A1 (en) * 2001-12-05 2003-06-05 Badenoch Scott Wilson Adaptive variable effort power steering system
US20070045020A1 (en) * 2005-09-01 2007-03-01 Martino Marc G Three-wheeled vehicle with centrally positioned motor and driver's seat
US20100228417A1 (en) * 2009-03-06 2010-09-09 Gm Global Technology Operations, Inc. Driver hands on/off detection during automated lane centering/changing maneuver

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11014607B2 (en) 2018-05-31 2021-05-25 Bombardier Recreational Products Inc. Steering system for a vehicle

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