FR2930197A3 - Roll control system for motor vehicle, has stabilizer bar connecting two wheels by connection device i.e. actuator, where actuator has electroactive elements e.g. electrostrictive element, and member connected to stabilizer bar - Google Patents

Abstract

The system has a stabilizer bar connecting two wheels by a connection device (11) i.e. actuator, where the actuator has electroactive elements (113-115) e.g. electrostrictive, magnetostrictive or piezoelectric elements. The actuator has members (111, 112) connected to the stabilizer bar and one of the wheels, respectively. The members are connected with each other when the electroactive element (113) is at rest. The actuator has a sensor (116) for measuring a relative position of the members. An independent claim is also included for a roll control method.

Description

System and method for controlling roll of a vehicle The invention relates to a roll control system of a vehicle for connecting a roll bar to the wheels of the vehicle. It also relates to a control method associated with such a system. An anti-roll bar is a mechanical element involved in the suspension of a vehicle. Two wheels of the vehicle on either side of a longitudinal axis of the vehicle are able to move substantially vertically relative to the body of the vehicle through a suspension system. Conventionally, the antiroll bar has two arms connected by a section adapted to be deformed by torsion and pivotally mounted on the body along a transverse axis. Each arm is connected via a link to a support wheel. Thus, when the vehicle is cornering, it tends to swing towards the outside by the depression of the outer wheel and the raising of the inner wheel. The anti-roll bar limits this trend. However, when the vehicle is in a straight line on a chaotic road, the anti-roll bar transmits the jolts that a wheel receives from the other wheel. This phenomenon is called copying, and it decreases the comfort of the passengers in the vehicle. To limit the copying phenomenon, it is proposed in WO 2005/120190 to replace at least one connecting rod connecting the wheel to the anti-roll bar by a hydraulic cylinder coupled to a control system for linking or not the anti-roll bar to the wheel. This system requires the use of a hydraulic circuit which poses maintenance problems and needs to take into account in particular the treatment of the fluid during the dismantling of the vehicle.

It is therefore an object of the invention to provide a roll control system of a vehicle that does not pose the maintenance and treatment problems specific to the dismantling of a hydraulic circuit.

With this objective in view, the subject of the invention is a system for controlling the rolling of a vehicle, the vehicle comprising at least two wheels on either side of a longitudinal axis of the vehicle, the wheels being mounted elastically movable relative to the vehicle for the suspension of the vehicle, the system comprising an anti-roll bar connecting the two wheels via a connection device. The connection device is an actuator comprising electro-active elements.

Thus, thanks to the invention, the control system operates entirely electrically, and it avoids the use of a hydraulic circuit, which no longer poses a problem of dismantling and maintenance.

According to an embodiment, the actuator comprises a first and a second member, the members being slidably mounted together, the first member being connected to the antiroll bar, the second member being connected to the wheel, a first member assets to bind the two members on command. When the two members are linked, they form a rod that gives all its functionality to the anti-roll bar. On the other hand, when the members are free to slide, the anti-roll bar no longer intervenes in the suspension, and the copying phenomenon is eliminated. In particular, the members are interconnected the first electro-active element is at rest. Thus, in the event of a power failure of the control system, the anti-roll bar is in use, which is safer for the handling of the vehicle, even if the copying phenomenon remains present. According to another option, the first active element can be arranged so that the limbs are free when the first electroactive element is at rest. The anti-roll bar is then decoupled from the wheels in case of power failure. This system design optimizes the use of energy by the system. According to an improvement, the actuator comprises a sensor capable of measuring the relative position of the limbs, a second electroactive element capable of binding on command a third electro-active element to one of the members, the third electroactive element being adapted to move the second electro-active element relative to the other member. Such a system is capable of providing relative movement between the first and second members by alternately clamping the first and second electroactive elements combined with elongation or retraction of the third electroactive element. By way of example, the electro-active elements are chosen from elements with magnetostrictive, electrostrictive or piezoelectric material.

Such material develops contraction or elongation when subjected to either a magnetic field or an electric field. An example of magnetostrictive material is Terfenol-D, an alloy of iron, terbium and dysprosium.

The possible elongation of the material is of the order of 0.2% with a bandwidth of the order of 15 kHz. The invention also relates to a control method of a system as described above, wherein the electro-active elements are controlled to bind the anti-roll bar to the wheels when the vehicle is in a bend. The anti-roll bar is therefore in operation when the vehicle is turning. In the case where the members are interconnected when the first electro-active element is at rest, the electro-active elements are controlled to bind the anti-roll bar to the wheels when the vehicle is in a straight line and on a smooth road. The comfort in the vehicle is not affected in these conditions by the commissioning of the anti-roll bar. In addition, it avoids the consumption of electrical energy to release the connection between the members.

According to a particular arrangement, it is determined that the road is smooth when a signal filtered by a high-pass filter of lateral acceleration information is less than a predetermined threshold. The lateral acceleration is representative of the shaking to which the vehicle is subjected, generated by the reliefs of the road on which the vehicle is traveling. The high-pass filter makes it possible to ignore turning situations.

For example, a cutoff frequency of the high pass filter is between 3 and 10 Hz. According to an improvement, to actuate the connection of the anti-roll bar to the wheels, the electro-active elements are progressively activated. The electro-active elements make it possible to control a deformation proportional to the stress. It is therefore possible to control a progressivity in switching between the free state and the linked state, for example with a switching time of the order of 1 s to 10 s. In the case of a control system with the second and the third electro-active element, it is possible to control the relative movement of the limbs towards a central position when the vehicle is at the end of a turn. If the limbs are tied to each other in a position different from a central position in which they would be when the vehicle is in equilibrium, the release of the limbs would cause an oscillation perceived negatively by the occupants of the vehicle. By gradually reducing the limbs to the central position in a controlled manner, this negative perception is avoided. The invention will be better understood and other features and advantages will become apparent on reading the description which follows, the description referring to the appended drawings in which: FIG. 1 is a schematic view of a roll control system according to the invention; Figure 2 is a schematic view of a connection device of the system of Figure 1; FIG. 3 is a schematic view of an electro-active element of the device of FIG. 2; Figure 4 is a variation of the system of the invention, Figure 5 is a block diagram of a control method of the system of the invention; FIG. 1 shows a system for controlling the roll of one to the invention. FIGS. 1 to 3 show two wheels of the vehicle, located on both sides of a vehicle. longitudinal axis, are resiliently mounted relative to the vehicle by conventional suspension means, not shown, except a slider 20 extending substantially vertically and provided with a spring 21. The system comprises an anti-roll bar 10 connecting 30 one of the sliders 20 via a connection device 11 and the other slider 20 by a rod 12. The anti-roll bar 10 has at its ends two arms 102. The bar 10 comprises a section 101 connecting the two arms 102 It is m pivoted on the body 3 by means of mounting bearings, not shown, along a transverse axis B and is adapted to be deformed by torsion. Referring to Figure 2, the connection device 11 comprises two members, the first member 111 being connected to the anti-roll bar 10, the second member 112 being connected to the wheel 2. The connections are made for example via of ball joints. The members 111, 112 are slidably mounted together.

A first electro-active element 113 makes it possible to bind on order the two members 111, 112 while preventing their sliding. The first electro-active element 113, acting as a brake, is detailed in FIG. 3. It comprises a first jaw 1131 fixedly mounted on the first member 111. It also comprises a second jaw 1132 opposite to the first 1131 relative to the second member. 112. The second jaw 1132 is fixed on one end of an electro-active bar 1130, the other end of said bar 1130 being fixed on the first member 111. The bar 1130 and the jaws 1131, 1132 are arranged so that when the bar 1130 is at rest, the jaws 1131, 1132 clamp between them the second member 112 so as to prevent its sliding. When the bar 1130 electro-active is activated, it extends and allows the release of the second member 112 so as to allow its sliding relative to the first member 111. The connection device 11 further comprises a second electro-active element 114 also comprising a second electro-active bar, not shown and two jaws 1141, 1142, of identical constitution to the first electroactive element 113. However, the second electroactive element 114 is attached to the end of the bar of a third electro-active element 115, said bar 1150 being mounted in the sliding direction of the second member 112. Thus, the third electro-active element 115 is able to modify the distance between the first 113 and the second electro-active element 114. The electro-active bars 1130, 1150 are for example magnetostrictive material, electrostrictive or piezoelectric. The connection device 11 further includes a sensor 116 capable of measuring the relative position of the members 111, 112. The control system 1 of the roll comprises a calculator, not shown, which can be dedicated, or which can also realize other functions. The computer receives as input, as shown in Figure 5, information on the position of the steering wheel steering vehicle, a Vv information on the speed of the vehicle and information yt lateral acceleration of the vehicle. This information, Vv, yt can come from dedicated sensors, but preferentially come from systems that perform other functions, such as a trajectory control system.

The calculator determines in a first functional block 51 whether the vehicle is in a cornering situation or not, depending on the angle of the steering wheel and the vehicle speed Vv. In parallel, in a second functional block 52, the transverse acceleration information yt is filtered by a high-pass filter and is compared with a predetermined threshold for delivering smooth road information if the filtered signal is below said predetermined threshold. A third functional block 53 receives the turn information and the smooth road information and deduces the commands to be sent to the electro-active elements 113, 114, 115. It controls that the first 113 and the second electro-active element 114 are turned off when the vehicle is cornering or the road is smooth. In this situation, the anti-roll bar 10 is coupled to the two wheels 2 and is fully functional.

In other words, the first and the second electro-active element 114 are activated when the vehicle is not turning at the same time as the road is chaotic. In this situation, the anti-roll bar 10 is decoupled from the wheels 2 and the suspensions of the vehicle act independently. During a transition from the linked state to the free state of the anti-roll bar 10, the third functional block 53 controls the relative movement of the limbs 111, 112 towards a central position. The position sensor 116 makes it possible to know the distance of the members 111, 112 to the central position and to determine which movement is to be controlled.

The linked state of the members 111, 112 is represented in step 0 of FIG. 6. When the displacement is controlled, several cycles are controlled, one of which is described below, steps 1 to 5.

In step 1, the activation of the first electro-active element 113 is controlled. The jaws 1131, 1132 of the first electro-active element 113 loosen and the members 111, 112 remain connected to each other by the second electro-active element 114. In step 2, the third electroactive element 115 is activated, which causes the first electroactive element 113 to move away from the second by a distance p. In step 3, the first electroactive element 113 is deactivated, which then binds to the second member 112. In step 4, the second electroactive element 114 is activated, which is released from the second member 112, and the third electroactive element 115 is deactivated, which causes the first electroactive element 113 to approach the second. In step 5, the second electroactive element 114 is deactivated, which links it to the second member 112. It is then in the same situation as in step 0, except that the two members 111, 112 have moved relatively to each other by a distance p. The frequency of the cycles which can follow one another is high, of the order of 10 to 15 kHz, which makes it possible to obtain a reasonable speed of displacement. When the vehicle is in a straight line and returns to a smooth road, the third block determines that it is necessary to establish the connection of the members 111, 112. It is then possible to control the first and the second electro-active element 114 in a progressive manner while decreasing the control signal of the electro-active elements for a duration of 0.5 to 10 s.

In a second embodiment, shown in Figure 4, the system 1 'comprises two connection devices 11, 11' as described above. It is thus possible to completely disconnect the anti-roll bar 10 and to reduce the mass associated with the wheels 2. The invention is not limited to the embodiments that have just been described by way of example only. The second 114 and the third electro-active element 115 can be suppressed by giving up the function of refocusing the members 111, 112.

Claims (11)

REVENDICATIONS1. Vehicle roll control system, the vehicle having at least two wheels (2) on either side of a longitudinal axis of the vehicle, the wheels (2) being mounted to move elastically relative to the vehicle for suspension of the vehicle, the system comprising an anti-roll bar (10) connecting the two wheels (2) via a connecting device (11), characterized in that the connecting device (11) is an actuator comprising elements electroactive substances (113, 114, 115). 2. System according to claim 1, wherein the actuator comprises a first (111) and a second member (112), the members (111, 112) being slidably mounted together, the first member (111) being connected to the anti-roll bar (10), the second member (112) being connected to the wheel (2), a first of the electro-active elements (113, 114) making it possible to bind the two members (111, 112) to order. 3. System according to claim 2, wherein the members (111, 112) are interconnected when the first electro-active element (113) is at rest. 4. System according to claim 2, wherein the actuator (11) comprises a sensor (116) capable of measuring the relative position of the limbs (111, 112), a second electro-active element (114) capable of binding on command a third electro-active element (115) to one of the members (112), the third electroactive element (115) being able to move the second electro-active element (114) relative to the other member (111). ). 5. The system of claim 1, wherein the electro-active elements (113, 114, 115) are selected from magnetostrictive, electrostrictive or piezoelectric material elements. 6. A method of controlling a system according to one of claims 1 to 5, characterized in that the electro-active elements (113, 114, 115) are controlled to bind the anti-roll bar (10) to the wheels (2). ) when the vehicle is turning. 7. A control method according to claim 6 of a system according to claim 3, wherein the electroactive elements are controlled to bind the anti-roll bar (10) to the wheels (2) when the vehicle is in a straight line and on a smooth road . 8. Control method according to claim 7, wherein it is determined that the road is smooth when a signal filtered by a high-pass filter of a lateral acceleration information is less than a predetermined threshold. 9. Control method according to claim 8, wherein a cutoff frequency of the filter passes high is between 3 and 10 Hz. 10. A control method according to claim 7, wherein, to actuate the release of the anti-roll bar (10) to the wheels (2), the electro-active elements (113, 114) are progressively actuated. 11. A control method according to claim 6 of a system according to claim 4, wherein one controls the relative movement of the limbs (111, 112) to a central position when the vehicle is out of turn.