Patent Application
20230331055
This patent application claims priority from Italian patent application no. 102022000007496 filed on Apr. 14, 2022, the entire disclosure of which is incorporated herein by reference.
The invention relates to a method to control an active shock absorber of a road vehicle.
The movement of passive shock absorbers is entirely determined by the stresses transmitted by the road surface and, therefore, passive shock absorbers are “at the mercy” of the road surface. For a few years now, active shock absorbers have been offered, which are capable of making autonomous movements (namely, completely independent of the stresses transmitted by the road surface), which are added to the movements caused by the stresses transmitted by the road surface; the aim of the autonomous movements made by an active shock absorber is that of reacting to the stresses transmitted by the road surface so as to maximize the dynamic performance of the road vehicle or improve the driving comfort of the road vehicle (the same road vehicle can have its active shock absorbers pursue different targets depending on the type of driving chosen by the driver).
An active shock absorber is provided with a hydraulic or electric shock absorber of its own, which can be controlled so as to generate an autonomous movement (namely, completely independent of the stresses transmitted by the road surface).
Patent application US2018134111A1 discloses a method to control the active shock absorbers of a car.
The object of the invention is to provide a method to control an active shock absorber of a road vehicle, which is capable of optimizing the damping response.
According to the invention, there is provided a method to control an active shock absorber of a road vehicle according to the appended claims.
The appended claims describe preferred embodiments of the invention and form an integral part of the description.
The invention will now be described with reference to the accompanying drawings showing a non-limiting embodiment thereof, wherein:
In
The road vehicle 1 is provided with a powertrain system (which is known and is not shown herein), which can comprise an internal combustion engine and/or one or more electric motors and can transmit a motion to the front wheels 2 and/or to the rear wheels 2.
A hub 3 (schematically shown in
According to
Each active shock absorber 6 comprises a position sensor 11 (for example, a potentiometer), which provides the relative position p of the two elements 7 and 8, namely the exact measure of how much the element 8 is translated relative to the element 7. Furthermore, each active shock absorber 6 comprises a position sensor 11 (for example, a rotary encoder), which provides the angular position α of the electric actuator 10. The road vehicle 1 comprises four vertical accelerometers 13, which are mounted on the hubs 3 of the wheels 2, namely are rigidly fixed to the hubs 3 of the wheels 2 in order to move with the hubs 3 of the wheels 2 in an integral manner. Each vertical accelerometer 13 is configured to measure a vertical acceleration az of the corresponding hub 3.
According to
The road vehicle 1 comprises an electronic control unit (“ECU”) 16, which, among other things, controls the actuators 10 of the active shock absorbers 6 in the ways described below; from a physical point of view, the control unit 16 can consist of one single device or of several devices, which are separate from one another and communicate through the CAN network of the road vehicle 1. The control unit 16 is connected (directly or indirectly through a BUS network of the road vehicle 1) to the position sensors 11 and 12 and to the accelerometers 13, 14 and 15.
According to
According to
Basically, the open-loop transfer function TF2 entails the force F generated by the actuator 10 (namely, the contribution C2 of the target force FTGT of the actuator 10) being substantially proportional to the speed v of translation between the two elements 7 and 8 of the active shock absorber 6; namely, it increases as the speed v of translation between the two elements 7 and 8 of the active shock absorber 6 increases. Indeed, the gain of the transfer function TF2 is measured in [Ns/m] as, by being multiplied by the speed v of translation (measured in [m/s]), it directly provides the contribution C2 of the target force FTGT of the actuator 10 (measured in [N]).
In other words, the contribution C1 is determined based on the sole vertical acceleration az of the hub 3 and using the open-loop transfer function TF1, which provides the contribution C1 based on the vertical acceleration az; similarly, the contribution C2 is determined based on the sole speed v of translation between the two elements 7 and 8 of the active shock absorber 6 and using the open-loop transfer function TF2, which provides the contribution C2 based on the speed v of translation. Hence, the control unit 16 determines the target force FTGT based on the vertical acceleration az of the hub 3 and based on the speed v of translation between the two elements 7 and 8 of the active shock absorber 6 by exclusively using open-loop transfer functions TF1 and TF2.
Basically, the contribution C1 determined based on the vertical acceleration az constitutes an inertia compensation, whereas the contribution C2 determined based on the speed v of translation between the two elements 7 and 8 of the active shock absorber 6 constitutes a damping compensation.
According to a preferred embodiment, the transfer functions TF1 and TF2 are variable as the frequency varies (generally, ranging from 0 to 50 Hz) and have a gain and a phase.
To sum up, the control unit 16 determines the target force FTGT for the actuator 10 of the active shock absorber 6 based on the vertical acceleration az of the hub 3 (directly measured by the vertical accelerometer 13) and based on the speed v of translation between the two elements 7 and 8 of the active shock absorber 6 (provided by the estimating block 17). The control unit 16 controls the actuator 10 of the active shock absorber 6 so as to pursue the target force FTGT; according to a preferred embodiment, the target force FTGT determined by the control unit 16 only and exclusively based on the vertical acceleration az of the hub 3 and on the speed v of translation between the two elements 7 and 8 of the active shock absorber 6 could be added to other target forces determined in other ways and so as to pursue other targets (as described, for instance, in Italian patent applications 102021000015170 and 102021000015182).
According to a preferred embodiment, the transfer function TF2 consists of a map of experimentally determined points. In particular and according to
The embodiments described herein can be combined with one another, without for this reason going beyond the scope of protection of the invention.
The control method described above has different advantages.
First of all, the control method disclosed above optimizes the damping response of the active shock absorber 6 (both in terms of effectiveness of the response and in terms of promptness of the response), though maintaining a hood level of comfort.
Furthermore, the control method disclosed above is particularly stable and safe as, by operating in open loop, it never risks triggering undesired oscillations.
Finally, the control method described above is simple and economic to be implemented, for it does not require either a significant calculation ability or a large memory space.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022000007496 | Apr 2022 | IT | national |
