DOWN-SHIFT ACCELERATION OVERSHOOT COMPENSATION IN AUTOMOTIVE ELECTRONIC LONGITUDINAL DYNAMICS CONTROL OF AUTONOMOUS MOTOR VEHICLES

Abstract

An automotive electronic longitudinal dynamics control system of a motor vehicle comprising a powertrain comprising a propulsor electronically controlled by an electronic engine control module and an automatic transmission electronically controlled by an electronic automatic transmission control module to transmit mechanical power generated by the propulsor to drive wheels of the motor vehicle and comprising an automatic gearbox having a plurality of gears with corresponding gear ratios. The electronic automatic transmission control module is designed to output data indicative of a currently engaged gear and a next engaged gear that will be engaged after the currently engaged gear. The electronic engine control module is designed to receive data indicative of an engine torque request and to responsively control the propulsor based on the received engine torque request to cause the propulsor to output an engine torque equal to the requested engine torque. The automotive electronic longitudinal dynamics control system is designed to: receive from the electronic automatic transmission control module data indicative of the currently engaged gear and the next engaged gear that will be engaged after the currently engaged gear; receive a reference longitudinal acceleration to be followed and a measured longitudinal acceleration; compute an engine torque request for the electronic engine control module based on a longitudinal acceleration error indicative of a deviation of the measured longitudinal acceleration from the reference longitudinal acceleration, on a control law and on the currently engaged gear and the next engaged gear.

Claims

1. An automotive electronic longitudinal dynamics control system (LDM) of a motor vehicle (MV); the motor vehicle (MV) comprises a powertrain (PWT) comprising a propulsor (P) electronically controlled by an electronic engine control module (ECM) and an automatic transmission (T) electronically controlled by an electronic automatic transmission control module (ATM) to transmit mechanical power generated by the propulsor (P) to drive wheels (W) of the motor vehicle (MV) and comprising an automatic gearbox (G) having a plurality of gears (g.sub.i) with corresponding gear ratios (R(g.sub.i)); the electronic automatic transmission control module (ATM) is designed to output data indicative of a currently engaged gear (g.sub.i) and a next engaged gear (g.sub.i+1) that will be engaged after the currently engaged gear (g.sub.i); the electronic engine control module (ECM) is designed to receive data indicative of an engine torque request (ET(t, g.sub.i)) and to responsively control the propulsor (P) based on the received engine torque request (ET(t, g.sub.i)) to cause the propulsor (P) to output an engine torque equal to the requested engine torque ((ET(t, g.sub.i)); the automotive electronic longitudinal dynamics control system (LDM) is designed to: receive from the electronic automatic transmission control module (ATM) data indicative of the currently engaged gear (g.sub.i) and the next engaged gear (g.sub.i+1) that will be engaged after the currently engaged gear (g.sub.i); receive a reference quantity indicative of a reference longitudinal dynamics (a.sub.ref(t)) to be followed and a measured quantity indicative of a measured longitudinal dynamics (a(t)); compute an engine torque request (ET(t, g.sub.i)) for the electronic engine control module (ECM) based on a longitudinal dynamics error (e.sub.a(t)) indicative of a deviation of the measured longitudinal dynamics (a(t)) from the reference longitudinal dynamics (a.sub.ref(t)), on a control law (f(e.sup.a(t), g.sub.i)) and on the currently engaged gear (g.sub.i) and the next engaged gear (g.sub.i+1); the automotive electronic longitudinal dynamics control system (LDM) is characterized in that it is further designed to: compute a current engine torque request (ET(t, g.sub.i)) based on the longitudinal dynamics error (e.sub.a(t)), the control law (f(e.sub.a(t), g.sub.i)) and the currently engaged gear (g.sub.i); compute a fit factor () based on the gear ratios (R(g.sub.i), R(g.sub.i+1)) of the currently engaged gear (g.sub.i) and the next engaged gear (g.sub.i+1); and compute an adjusted engine torque request (ET(t, g.sub.i+1)) based on the current engine torque request (ET(t, g.sub.i)) and the fit factor ().

2. The automotive electronic longitudinal dynamics control system (LDM) of claim 1, wherein the fit factor () is computed based on a ratio between the gear ratios (R(g.sub.i), R(g.sub.i+1)) of the currently engaged gear (g.sub.i) and the next engaged gear (g.sub.i+1).

3. The automotive electronic longitudinal dynamics control system (LDM) of claim 1, wherein the adjusted engine torque request (ET(t, g.sub.i+1)) is computed based on a product of the current engine torque request (ET(t, g.sub.i)) and the fit factor ().

4. The automotive electronic longitudinal dynamics control system (LDM) of claim 1, wherein the control law (f(e.sub.a(t), g.sub.i)) comprises an integral action designed to provide an integral contribution to the engine torque request (ET(t, g.sub.i)) proportional to the integral of the longitudinal acceleration error (e.sub.a(t)); the automotive electronic longitudinal dynamics control system (LDM) is designed to implement an anti-wind-up system designed to gradually desaturate the integral action of the control law (f(e.sub.a(t), g.sub.i)); and the anti-wind-up system is designed to operate based on the fit factor ().

5. The automotive electronic longitudinal dynamics control system (LDM) of claim 1, wherein the reference quantity is indicative of a reference longitudinal acceleration (a.sub.ref(t)) and the measured quantity is indicative of a measured longitudinal acceleration (a(t)).

6. The automotive electronic longitudinal dynamics control system (LDM) of claim 5, further comprising two nested control loops with an external loop designed to control the longitudinal speed of the motor vehicle (MV) and an internal loop designed to control the longitudinal acceleration of the motor vehicle (MV); the external control loop is configured to receive a reference longitudinal speed (v.sub.ref(t)) to be followed and a measured longitudinal speed (v(t)) and to output a reference longitudinal acceleration (a.sub.ref(t)) for the internal control loop based on a longitudinal speed error (e.sub.v(t)) indicative of a deviation of the measured longitudinal velocity speed (v(t)) from the reference longitudinal speed (v.sub.ref(t)) and on a control law (f.sub.v(t)); the internal control loop is configured to receive the reference longitudinal acceleration (a.sub.ref(t)) from the external control loop and a measured longitudinal acceleration (a(t)) and to output an engine torque request (ET(t)) for the electronic engine control module (ECM) based on a longitudinal acceleration error (e.sub.a(t)) indicative of a deviation of the measured longitudinal acceleration (a(t)) from the reference longitudinal acceleration (a.sub.ref(t)) and on a control law (f.sub.a(t)).

7. An automotive electronic control system (ECS) of a motor vehicle (MV) comprising a powertrain (PWT) comprising a propulsor (P) and an automatic transmission (T) to transmit mechanical power generated by the propulsor (P) to drive wheels (W) of the motor vehicle (MV), and comprising an automatic gearbox (G) having a plurality of gears (g.sub.i) with corresponding gear ratios (R(g.sub.i)); the automotive electronic control system (ECS) comprises: an electronic automatic transmission control module (ATM) designed to output data indicative of a currently engaged gear (g.sub.i) and a next engaged gear (g.sub.i+1) that will be engaged after the currently engaged gear (g.sub.i); an electronic engine control module (ECM) designed to receive data indicative of an engine torque request (ET(t, g.sub.i)) and to responsively control the propulsor (P) based on the received engine torque request (ET(t, g.sub.i)) to cause the propulsor (P) to output an engine torque equal to the requested engine torque request (ET(t, g.sub.i)); and the automotive electronic longitudinal dynamics control system (LDM) of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 shows a block diagram of an automotive powertrain.

[0028] FIG. 2 shows time trends of automotive quantities involved in the longitudinal dynamics control of an autonomous motor vehicle according to the prior art.

[0029] FIG. 3 shows a block diagram of an electronic longitudinal dynamics control of an autonomous motor vehicle according to the present invention.

[0030] FIG. 4 shows time trends of automotive quantities involved in the longitudinal dynamics control of an autonomous motor vehicle according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0031] The present invention will now be described in detail with reference to the accompanying figures in order to enable a person skilled in the art to manufacture it and use it. Various modifications to the described embodiments will be immediately evident to those skilled in the art and the general principles described can be applied to other embodiments and applications without thereby departing from the scope of protection of the present invention, as defined in the appended claims. Therefore, the present invention is not to be considered limited to the described and illustrated embodiments, but it must be conceded the broadest scope of protection in line with the described and claimed characteristics.

[0032] Unless defined otherwise, all the technical and scientific terms used herein have the same meaning as commonly used by persons of ordinary experience in the pertinent field of the present invention. In the event of conflict, the present description, comprising the provided definitions, shall be binding. Furthermore, the examples are provided for the purposes of illustration only and as such are not to be considered limiting.

[0033] In particular, the block diagrams included in the accompanying figures and described in the following are not to be understood as representations of the structural characteristics, i.e. as constructional limitations, but are to be interpreted as representations of functional characteristics, i.e. features intrinsic to the devices and defined by the effects obtained, i.e. as functional limitations, and which can be implemented in different manners, i.e. so as to safeguard the functionalities of the device (its ability to function).

[0034] In order to facilitate the comprehension of the embodiments described herein, reference will be made to some specific embodiments and a specific language will be used to describe the same. The terminology used in the present document is only intended to describe particular embodiments and is not intended to limit the scope of the present invention.

[0035] The present invention is essentially based on the idea of adapting the engine torque request to the ECM by exploiting information from the ATM, which, in addition to the classic information regarding the currently engaged gear g.sub.i, also provides information regarding the next engaged gear g.sub.i+1 that will be engaged after the currently engaged gear.

[0036] In particular, the following equation can be written based on the wheel torque equilibrium principle:

[00001]$\mathrm{ET}\left(t,g_i\right).Math.R\left(g_i\right)=ET\left(t,g_{i+1}\right).Math.R\left(g_{i+1}\right)$

where R(g.sub.i) is the gear ratio of the currently engaged gear g.sub.i and R(g.sub.i+1) is the gear ratio of the next engaged gear g.sub.i+1 that will be engaged after the currently engaged gear.

[0037] From this equation, it is thus possible to obtain the following:

[00002]$\mathrm{ET}\left(t,g_{i+1}\right)=\frac{R\left(g_i\right)}{R\left(g_{i+1}\right)}.Math.\mathrm{ET}\left(t,g_i\right)$

wherein ET(t, g.sub.i+1) represents an adjusted torque request that would need to be sent to the ECM in the event that the next engaged gear g.sub.i+1 is engaged instead of the currently engaged gear g.sub.i, and the ratio

[00003]$\frac{R\left(g_i\right)}{R\left(g_{i+1}\right)},$

indicated in the following as for the sake of brevity, represents a fit factor which can be used to adapt the engine torque request ET(t, g.sub.i) computed by the LDM based on the currently engaged gear g.sub.i in order to take into account the gear shift that the ATM will command, i.e., the next engaged gear g.sub.i+1 that will be engaged after the currently engaged gear g.sub.i. In this manner, the engine torque request ET(t, g.sub.i), which in the state of the art would give rise to above-described acceleration overshoot as a result of the downshifting carried out by the automatic gearbox in a pickup phase, is adjusted by a factor which takes into account such a downshifting and which in particular is proportional to the ratio between the speed ratios R(g.sub.i) and R(g.sub.i+1) of the currently engaged gear g.sub.i and the next engaged gear g.sub.i+1 that will be engaged after the currently engaged gear.

[0038] In a downshifting phase, in fact, the speed ratio R(g.sub.i) of the currently engaged gear g.sub.i is lower than the speed ratio R(g.sub.i+1) of the next engaged gear g.sub.i+1 that will be engaged after the currently engaged gear, which results in a fit factor lower than the unit that accordingly reduces the engine torque request ET(t, g.sub.i) that otherwise would have been sent to the ECM, thus significantly reducing the acceleration overshoot caused by the downshifting carried out by the automatic transmission in a pickup phase, with clear benefits for the perceived driving comfort of the driver and passengers of the vehicle.

[0039] The person skilled in the art may appreciate that the fit factor could be computed based on the gear ratios R(g.sub.i) and R(g.sub.i+1) of the currently engaged gear g.sub.i and the next engaged gear g.sub.i+1 using a different function, also more complex than the one indicated above, which is anyway suitable for achieving the same object, i.e., adapting the engine torque request ET(t, g.sub.i) so as to take into account the next gear shift.

[0040] Merely by way of example, the fit factor could be computed based on, in particular the ratio between, the engine regimes (rpms) with the currently engaged gear g.sub.i and the next engaged gear g.sub.i+1.

[0041] Similarly, the person skilled in the art may also appreciate that the engine torque request ET(t, g.sub.i) could be adjusted based on the fit factor in a manner different from the one indicated above.

[0042] For example, the fit factor A, instead of simply multiplying the engine torque request ET(t, g.sub.i), could be used as an anti-wind-up in the control law f(e.sub.a(t), g.sub.i) of the controller implemented by the LDM.

[0043] In fact, as is known, in controllers in a PI or PID configuration, typically but not necessarily implemented by the internal longitudinal acceleration control loop, the proportional action makes a contribution to the output represented by the engine torque request ET(t, g.sub.i) proportional to the longitudinal acceleration error e.sub.a(t) via a constant K.sub.P called proportional gain; the integral action makes a contribution to the engine torque request ET(t, g.sub.i) proportional to the integral of the longitudinal acceleration error e.sub.a(t), therefore proportional to its average value, via a constant Kr equal to the inverse of an integral time constant T.sub.I, also called reset time, multiplied by the proportional gain K.sub.P; and the derivative action makes a contribution to the engine torque request ET(t, g.sub.i) proportional to the derivative of the longitudinal acceleration error e.sub.a(t), therefore proportional to its variation over time, via a constant K.sub.P equal to a derivative time constant T.sub.P multiplied by the proportional gain K.sub.P.

[0044] It is likewise known that actuators used in control systems have constraints to the amplitudes of the outputs, which cannot exceed maximum and minimum limits. Typically, in fact, an actuator has an input/output characteristic with a linear intermediate section and two saturation sections arranged on opposite sides of the linear section and at which the actuator output assumes respective minimum and maximum saturation limits independently of the amplitude of the input.

[0045] When a controller with integral action is used, it is possible for the actuator output to reach the maximum and minimum saturation limits and in such a case, although the integral action continues to increase also in the presence of a non-zero longitudinal acceleration error e.sub.a(t), this increase has no effect on the response of the controlled system.

[0046] Besides making the actuator not function correctly, this operating situation also renders it inactive when the error decreases or its sign is inverted; in fact, the controller is only able to reactivate itself when the actuator output re-enters the linearity zone of its input/output characteristic (desaturation of the integral term). This phenomenon is commonly called integral wind-up.

[0047] The wind-up phenomenon can be remedied using so-called anti-wind-up techniques, i.e., anti-saturation or desaturation techniques for hindering a saturation of the actuator outputs.

[0048] A first anti-wind-up technique is known by the initials IMC, an acronym for Internal Model Control, since a model of the process to be controlled is required, the model of the process to be controlled is internal to the controller and the controller uses the model of the process to be controlled to enhance performance. In essence, the operation of this anti-wind-up technique is based on the assumption that the process to be controlled is known so that it is possible to obtain a copy of the same and integrate said copy in the controller.

[0049] A second anti-wind-up technique consists in the desaturation of the actuator outputs via the interruption of the integral action as soon as the output u(t) of the controller reaches the saturation level of the actuator.

[0050] A third anti-wind-up technique consists, on the other hand, in the back-computation of the integral action via the introduction of a term e.sub.r(t) that is equal to the difference between the actuator output v(t) and the controller output u(t), which constitutes the actuator input or command, i.e., e.sub.r(t)=v(t)u(t), and which is returned to the input of the integral block and subtracted from the error e(t). This will yield a zero value which, as a result, will not affect the control in any way if the actuator is working within the saturation limits, whereas, when these limits are exceeded, a value will be generated which will help dampen the growth of the integral action.

[0051] A fourth anti-wind-up technique is the one disclosed in Italian patent application No. 102021000025079 filed on 30 Sep. 2021 by the Applicant, the contents of which are incorporated herein in their entirety by reference.

[0052] For example, in the anti-wind-up technique with back-computation of the integral action, the fit factor 2 could be used to gradually desaturate the integral action desaturation with a term computed as follows:

[00004]${\mathrm{Gain}}_{\mathrm{anti}-\mathrm{wind}-\mathrm{up}}.Math.\left(\mathrm{ET}\left(t,g_i\right).Math.-\mathrm{ET}\left(t,g_i\right)\right)\mathrm{where}$$\mathrm{ET}\left(t,g_i\right).Math.=\mathrm{ET}\left(t,g_{i+1}\right)$

[0053] The basic idea of the present invention described in the foregoing is illustrated schematically in FIG. 3, which shows a block diagram of an automotive electronic system, indicated as a whole by ECS, of an autonomous motor vehicle MV.

[0054] The automotive electronic system ECS comprises: [0055] the ECM, which receives data indicative of an engine torque request ET(t, g.sub.i) and responsively controls the propulsor P based on the engine torque request ET(t, g.sub.i) to cause the propulsor P to output an engine torque equal to the requested engine torque; [0056] the ATM, which outputs data indicative of the currently engaged gear g.sub.i and the next engaged gear g.sub.i+1; and [0057] the LDM, of which only the internal longitudinal acceleration control loop, typically with integral action, i.e., of a PI or PID type, is shown in FIG. 3 for the purposes of illustration, which LDM is designed to: [0058] receive from the ATM data indicative of the currently engaged gear g.sub.i and the next engaged gear g.sub.i+1; [0059] receive from the external longitudinal speed control loop (not shown) a reference longitudinal acceleration a.sub.ref(t) to be followed; [0060] receive from the automotive communication network the measured longitudinal acceleration a(t) of the motor vehicle MV; [0061] compute the aforementioned fit factor based on the gear ratios R(g.sub.i) and R(g.sub.i+1) of the currently engaged gear g.sub.i and of the next engaged gear g.sub.i+1 that will be engaged after the currently engaged gear; and, [0062] compute the engine torque request ET(t, g.sub.i+1) based on a longitudinal acceleration error e.sub.a(t) indicative of a deviation of the measured longitudinal acceleration a(t) from the reference longitudinal acceleration a.sub.ref(t), on the currently engaged gear g.sub.i, on the next engaged gear g.sub.i+1 and on the control law f(e.sub.a(t), g.sub.i) of the controller implemented by the LDM, typically a controller with integral action, i.e., of a PI or PID type.

[0063] In particular, in the above-described embodiment, the fit factor is computed as a ratio between the gear ratios R(g.sub.i) and R(g.sub.i+1) of the currently engaged gear g.sub.i and of the next engaged gear g.sub.i+1 that will be engaged after the currently engaged gear.

[0064] In a different embodiment, the fit factor could be computed using different functions.

[0065] Furthermore, in the above-described embodiment, the current engine torque request ET(t, g.sub.i) is adjusted by first computing a current engine torque request ET(t, g.sub.i) based on the longitudinal acceleration error e.sub.a(t), on the control law f(e.sub.a(t), g.sub.i) of the controller implemented by the LDM, typically of a PI or PID type, and on the currently engaged gear g.sub.i, and then computing an adjusted engine torque request ET(t, g.sub.i+1) based on the current engine torque request ET(t, g.sub.i) and the fit factor 2.

[0066] In a different embodiment, the current engine torque request ET(t, g.sub.i) could be adjusted using different functions that take into account the next gear shift between the currently engaged gear g; and the next engaged gear g.sub.i+1.

[0067] The benefits that the present invention allows to achieve are depicted in FIG. 4, which shows time trends of the same automotive quantities shown in FIG. 2, both with and without the implementation of the present invention. With particular reference to the longitudinal acceleration (third graph from the top), it may be appreciated in the first half of the time scale the significant reduction in longitudinal acceleration overshoot obtained by means of the implementation of the present invention while, in the second half of the time scale, it may be appreciated the significant increase in longitudinal acceleration overshoot obtained without the implementation of the present invention.