WO2016177945A1

WO2016177945A1 - Method for controlling the position of a clutch control member

Info

Publication number: WO2016177945A1
Application number: PCT/FR2016/050746
Authority: WO
Inventors: Abdelmalek Maloum; Ludovic MERIENNE
Original assignee: Renault S.A.S
Priority date: 2015-05-05
Filing date: 2016-04-01
Publication date: 2016-11-10
Also published as: FR3035936A1; FR3035936B1

Abstract

The invention relates to a method for controlling the movement of a clutch control element (4) by means of an irreversible actuation system consisting of an electric actuating motor (1) connected by mechanical transmission means (2, 3) to the clutch control element, by sending a reference voltage (U^ref) from the electric motor, which allows the control element to be moved at all times from an initial position (x) to a reference position (x_ref), characterised in that the reference voltage (U^ref) is obtained by the integration of a value calculated from its own time derivative.

Description

METHOD FOR CONTROLLING THE POSITION OF A CONTROLLER

CLUTCH

The present invention relates to the control of robotized gearboxes, equipped with at least one clutch for interrupting the transmission of torque between a drive motor and the shifting mechanism of the box.

More precisely, it relates to a method for controlling the movement of a clutch control element by an irreversible actuation system composed of an electric actuation motor connected by mechanical transmission means to the element. clutch control.

This method is based on sending to the electric motor, a reference voltage, which allows each moment to move the control element from an initial position to a reference position.

In robotized gearboxes, clutch control can be provided by an electric or hydraulic control system controlled by a computer. FIG. 1 non-restrictively illustrates the irreversible actuating system, consisting of an electric actuating motor 1 and a motion transmission system composed of a set of gears (housed under a casing 2), which transmit the movement of the electric motor on a screw-nut system 3 which converts the rotational movement of the motor 1 into a translation movement of a clutch control cable 4, which "pulls" on a clutch lever ( not shown). Finally, an assistance spring 6 stores energy at closing the clutch, and restores it by helping to open the clutch.

In order to ensure a controlled transmission of the torque of the engine to the gearbox, the position of the cable must be controlled with an accuracy of about 0.1 mm. However, the peculiarity of such an actuation system is its irreversibility, linked to the high level of friction between the screw and nut. This feature keeps the system in position, in case of failure of the control of the electric motor (voltage drop for example). But it poses a problem of control, because its control is not linear: as long as the electric motor does not provide a level of effort superior to the friction, the system remains immobile, but once this level of effort exceeded, the system can get moving very quickly.

The level of friction can reach 70 to 80% of the maximum effort of the electric motor, and can vary according to the wear of the clutch, as indicated by way of example, on the curves of FIG. figure allows to compare the force curves (in Nm) on the stroke of the clutch stop (in millimeters), in the direction of its opening (disengaging) and its closing (clutch) for a clutch in the state nine (curves in dashed lines) and for worn clutch (curves in solid lines). It is found that the maximum additional effort to be provided with a worn clutch is greater in the direction of closure, because it must compensate in addition the wear of the return spring, which facilitates the closing of the clutch in the state new.

When trying to control the transmission of the engine torque to the gearbox, no exceeding of the cable position is permissible. This requirement makes the use of conventional control techniques (PID type) unsuitable for controlling the position of the cable. An object of the present invention is to move the clutch cable in a completely transparent manner to the driver during clutch and clutch operations. The desired accuracy is 0.005 mm. It must be respected, without exceeding the position of the cable, nor know the effort that must exert the electric motor to overcome the friction.

In addition to these mechanical constraints, the control must respect thermal constraints. To ensure the durability of the electrical system, it must in particular avoid overly messy or sudden stresses on the motor 1, responding to repeated voltage jumps or excessive currents.

Finally, at the end of the closing of the clutch, the "licking" phase, where the torque of the heat engine is transmitted gradually to the gearbox, must be as transparent as possible, to avoid torque surges. . The movement of the clutch cable must therefore be controlled with an accuracy of 0.005, mainly during the licking phase, and without exceeding. The control must also be as continuous as possible, avoiding strong long current draws, in the engine.

The control input is generally a reference voltage of the actuating motor. The known calculation methods for the reference voltage, aim to minimize at every moment the difference between the actual position of the control element of the clutch, and the reference position it must reach. However, they most often generate a discontinuous voltage control, which has the disadvantage of strongly biasing the actuator, at the risk of causing overheating of the electric motor.

In summary, the main difficulties to overcome to control the movement of a control element such as a clutch cable by an irreversible actuating system consisting of an electric motor connected by mechanical transmission means to the control of 'clutch, are:

to overcome the friction which is nonlinear, the desired static precision, which is 0.005 mm, to ensure small displacements (of the order of 0.1 mm) without overshooting, to eliminate the main sources of jerking. torque in clutch licking phase, and limit the risk of overheating or breakage of the electrical system.

The present invention aims to overcome these difficulties, to control the position of a robotized box clutch. For this purpose, it proposes that the reference voltage be obtained by integrating a calculated value of its own derivative in time.

Preferably, the derivative of the reference voltage includes a first term of difference between the state and the position setpoint of the control element, a second term of difference between the state and the setpoint of its speed, and a third term of difference between the state and the setpoint of the derivative of its speed.

Integrating the first gap term gives a compensation term representing the resistive torque of the system; the integration of the second term of difference gives a proportional term on a position error; the integration of the third term gives a proportional term on a speed error.

The present invention will be better understood on reading the following description of a nonlimiting embodiment thereof, with reference to the appended drawings, in which:

FIG. 1 represents an electric clutch control system,

FIG. 2 shows the differences of forces involved on a clutch opening and closing stroke depending on its state, and

Figure 3 shows position curves, control voltage and motor current when closing a clutch.

An electric motor such as that illustrated in FIG. 1 is represented by the following equations: electric equation of the motor

mechanical equation of displacement of

the clutch, with

T _d : Resisting torque of the electric motor (unknown exogenous input, considered as a disturbance);

J: Inertia of the electric motor;

/: Current of the armature of the electric motor;

k: Coefficient of the voltage induced by the electric motor; R: Resistance of the armature of the electric motor;

L: Inductance of the armature of the electric motor;

U ^{ref The} reference voltage that we want to apply to the terminals of the electric motor, it is between U ^min and U ^max

(typically, U ^max will be the voltage of the on-board network);

The resisting torque of the electric motor T _d = f (x) is a function of the position x of the clutch cable. It depends on the force applied by the screw-nut system, the force of the return spring, and the force applied by the diaphragm of the clutch. This effort also varies according to the degree of wear of the clutch. Various sensors measure the position of the cable x, which is between two stops (open and closed position), as well as the speed of a point of the cable of

the clutch. A current sensor is also available to provide a measurement of the armature current of the DC motor.

The proposed control strategy aims at moving the clutch cable from an initial position x to a reference position x ^ref , to satisfy the conditions of a perfect gearshift in the gearbox, while ensuring the holding of the electrical system. The cable displacement control input is the reference voltage of the electric motor U ^ref which provides this displacement. From the two equations above, the system with respect to the position to be regulated can be written:

In known controller synthesis methods, for example, a proportional type regulator (PID) is used. In the present case, such a regulator does not prove to be optimal with respect to the orders of magnitude of the system, since the resisting torque that can be compensated can be very large and imposes excessive gains in these conditions. To obtain a more continuous control, the invention proposes to take into consideration an additional physical quantity, such as the derivative of the U ^ref command. The system can then be written as follows:

With such an extended system, the main control becomes the derivative of the voltage to be applied to the actuating motor. According to the invention, the reference voltage U ^ref is then obtained by integrating a calculated value of its own derivative in time. This ensures a greater continuity of the control synthesized by the regulator. In addition, the disturbance to compensate is no longer U ^ref , but its derivative, which has the advantage of reaching zero when stopping moving the clutch. We take advantage of the property of the function that can not vary at x

constant . To use this extended system, one preferably chooses a method which takes into account the gains on the differences between the states and the instructions on the position of the cable.

speed v - v _re f. The derivative of the reference voltage U _re then preferably includes a first term of difference between the state and the position reference of the control element.

second term of difference between the state and the setpoint of its speed (V _ref - v), and a third term of difference between the state and the reference of the derivative of its speed.

first term of deviation gives a compensation term representing the resistive torque of the system, the integration of the second term deviation gives a proportional term on a position error. The integration of the third term gives a proportional term on a speed error. The reference voltage U _re f is then equal to the sum of the first three proportional terms, and a fourth additional term proportional to the current I.

Lyapunov's theory makes it possible, for example, to create a regulator that meets these criteria, and that has the additional advantage of having a single adjustment parameter, which considerably simplifies the debugging phase (MAP) of the regulator. This theory is therefore particularly appropriate. However, without departing from the scope of the invention, it is possible to use other efficient calculation methods, provided that all the deviation terms and the proportional terms depend only on a single adjustment parameter.

By naming λ the tuning parameter in the Lyapunov equation, the following regulator is obtained on the derivative of the control voltage, in which gains on the deviation of position, velocity and acceleration depend on the

only parameter λ:

By integration, we deduce the voltage command U _ref to apply:

In this command, the first term is proportional to the integral of the position difference. It makes it possible to compensate for the resistant torque of the system T _d (whether it is in the worn or new state). The second term is proportional to the position error. The third term is proportional to a speed error. The last term, termed "feed-forward", serves to increase the current dynamics.

In summary, the method makes it possible to control the movement of a clutch control element by an irreversible actuation system composed of an electric actuation motor connected by mechanical transmission means to the clutch control element. , by sending to the electric motor a reference voltage U ^ref , which allows each moment to move the control element, from an initial position x to a reference position x _ref . The various steps of calculating the command at time t are for example the following:

a) We receive all the measurements and instructions: I (t), x (t), x ^ref (t) and v (t),

b) The velocity reference trajectory is calculated by deriving the reference position, ie x ^ref (t) = x ^ref (t) - x ^ref (t-1).

This choice of reference trajectory calculation is simple, and has different advantages. First of all, when the position set varies abruptly, we have a pulse of

V] itesse x ^ref (t), which means that we instantly target a high speed which cancels immediately after, if the position setpoint does not vary, thus limiting the risk of overtaking. This is the case during the first phase of closing the clutch, between t = 0.1 and t = 0.15 on the first curve of Figure 3. The second advantage appears when x ^ref (t) varies slightly for example in the clutch licking phase that follows. In this case, we have a speed pulse x ^ref (t) which makes it possible to follow exactly the trajectory corresponding to x ^ref (t). If x ^ref (t) varies linearly, we have a constant target speed, which makes it possible to better follow the evolution of the position reference.

c) The integral control term is incremented:

This integral term serves to compensate for the evolution of the resistive torque of the electric motor. It is essential to separate the compensation from this torque, with the torque necessary for tracking. Since the resistive torque is a function of the position (and not of the speed), it is necessary to integrate the position error to better compensate for this term. The torque required to maintain the speed of the motor can be calculated by the loop on the speed error, as follows: d) We update the errors in position and speed

e) We calculate the new command to apply:

The setting of the parameter λ is obtained by making the orders of magnitude of the terms of the equation of step 5 consistent. By setting the parameter λ to 50, the implementation of this command on a clutch system gives the performance illustrated by way of example by the curves of Figure 3. On the first graph, the position of the clutch position is dashed, and the position measured in solid line. The case presented is a case of licking the clutch where it is necessary to regulate as finely as possible the position to ensure the most comfortable passage for the driver. We can see the rapid response of the actuator, when the instruction suddenly passes from 0 to 4.5mm to start licking and a follow-up within 0.1mm of the setpoint, when it varies around the point of licking.

The U ^ref command applied for this type of displacement is represented on the second graph, for a case of available voltage of 10V. We see the fast transition to 10V to respond quickly to the set point. During the monitoring phase, very little voltage is used and very little current as can be seen in the last graph which avoids the heating of the motor and the power electronics during the licking phase. This can last for several seconds, the regulator obtained meets the objective of limiting the heating of the control device.

This calculation uses only one setting parameter. It offers the advantage of always having the right ratio between the evolution of the different terms of the equation. The three control terms taking into account the position and speed errors are thus automatically made coherent, if it is desired to vary the movement dynamics of the actuator. This makes it possible to always ensure the separation of the calculations of the trajectory tracking and compensation terms of the resistive torque. If it is desired to increase the movement dynamics of the actuator, it is possible for example to increase the value of the parameter A. This increases the dynamics of evolution of the error terms in position and in speed. The dynamics of evolution of the integral term is also increased to the most just, to overcome the fact that, if the actuator moves faster, the resistant torque can also evolve faster.

By maintaining a great stability of regulation over a wide range of value of the parameter λ, it is possible to overcome the constraints of stability for the calibration of the regulator. Under these conditions, the only criterion remaining to be optimized is the level of current and voltage used during the licking phase. The objective is then to calibrate the term λ as low as possible while checking the fact of always staying in a range of +/- 0.005mm around the setpoint. The objective may be, for example, to never exceed 10A in the engine during licking phases, which can last up to several seconds. An appropriate method is to start by setting the term λ to a high value and then to decrease this value until it is possible to respect the constraint on the current used during the licking phase.

In conclusion, the synthesis of the regulator according to the Lyapunov theory offers appreciable advantages for the development. However, without departing from the scope of the invention, other theories can be applied, to the extent that they allow to synthesize a corrector for a system extended to the derivative of the control voltage.

Claims

Method for controlling the movement of a clutch control element (4) by an irreversible actuating system consisting of an electric actuating motor (1) connected by mechanical transmission means (2, 3) to the clutch control element (4), by sending to the electric motor a reference voltage which allows each

instant of moving the control element (4) from an initial position (x) to a reference position (x _ref ), characterized in that the reference voltage (U ^ref ) is obtained by integration of a value calculated from its own time derivative, including a first discrepancy term between the state and the control element position setpoint (x _re f - x), a second difference term between the state and the setpoint of its speed (V _ref - v), and a third term of difference between the state and the setpoint of the derivative of its speed

2. Control method according to claim 1, characterized in that the integration of the first term deviation gives a compensation term representing the resisting torque of the system, the integration of the second term deviation gives a proportional term on a position error, and the integration of the third term gives a proportional term on a speed error.

3. Control method according to claim 2, characterized in that the reference voltage (U _ref ) is equal to the sum of the first three proportional terms and a fourth additional term proportional to the current (J).

4. Control method according to claim 1, 2 or 3, characterized in that all the terms of deviations and the proportional terms depend only on a single adjustment parameter (λ).

5. Control method according to one of the preceding claims, characterized in that it comprises the following steps: all measurements and setpoints of current, reference position position and speed are received:

the velocity reference trajectory is calculated by deriving the reference position, either

the integral control term is incremented:

and

we update the errors in position and speed

6. Control method according to claim 5, characterized in that it comprises the following step of calculating the new control voltage (t) to be applied: