Method for regulating the control of an electrical wastegate actuator by measuring the current passing through the electrical actuator

Abstract

Method for regulating the control of an electrical wastegate actuator controlled via an H bridge to permit displacement of the wastegate in its closure and opening directions according to whether the current passes through the actuator in one or opposite direction, includes: determining a set position which the wastegate has to reach, and an activation time of the actuator defining a monitoring time; applying a control signal to the actuator to displace the valve into the set position; measuring the current passing through the H bridge and applying a correction factor to the current to obtain the motor torque; obtaining the displacement speed of the wastegate by integration of the motor torque; obtaining the position reached by the wastegate at the end of the monitoring time by integration of the speed; comparing the position reached with the set position; and repeating the method until the set position is reached.

Claims

1. A method for regulating the control of an electrical actuator of a valve permitting the exhaust gases of an internal combustion engine to be diverted from a fluid supply circuit of a turbine of a turbocharger designed to compress the fresh gases admitted into an air intake circuit of said internal combustion engine, said electrical actuator being controlled by means of an H bridge in order to permit a displacement of the valve in the direction of its closure and in the direction of its opening according to whether the current passes through the electrical actuator in one direction or in the opposing direction, characterized in that the method comprises the following steps: step 1: determining a set position (P.sub.c) which said valve has to reach from a known position (P.sub.ref) thereof and an activation time of said electrical actuator of the valve defining a monitoring time (t.sub.p), step 2: applying a control signal to the electrical actuator of said valve via said H bridge during said monitoring time (t.sub.p) to displace the valve into said set position, step 3: measuring the electrical current [i(t)] which passes through the H bridge during the monitoring time (t.sub.p) and applying a correction factor (Km) to said measured electrical current [i(t)] so as to obtain the motor torque (Cm) delivered by the electrical actuator during said monitoring time (t.sub.p), step 4: obtaining a speed [w(t)] of displacement of the valve during said monitoring time (t.sub.p) by the integration of said motor torque (Cm) over said monitoring time (t.sub.p), step 5: obtaining a position reached (Pt.sub.p) by the valve at the end of the monitoring time (t.sub.p) by the integration of the speed [w(t)] over said monitoring time (t.sub.p), step 6: comparing said position which has been reached (Pt.sub.p) with said set position (P.sub.c), step 7: repeating the method from step 2 until said set position (P.sub.c) is reached.

2. The method as claimed in claim 1, in which displacement stops of said valve, in the extreme open and closed positions, are ascertained by means of a detector of current thresholds passing through the H bridge, respectively for one direction of displacement and the opposing direction of displacement of the electrical actuator, in order to ascertain at least one initial reference position of the valve to establish said known position (P.sub.ref) thereof.

3. The method as claimed in claim 2, in which an unwanted blockage of the valve between said extreme closed and open positions, the extreme open positions being excluded, is detected by means of said detector of the current thresholds passing through the H bridge.

4. The method as claimed in claim 1, further comprising a step consisting of using the information about the value of the air pressure present in the air intake duct of the internal combustion engine provided by an air pressure sensor (PUT) arranged upstream of a butterfly valve for controlling the flow rate of air admitted into said engine, in order to verify if said set position (P.sub.c) corresponds to the supercharging pressure (P.sub.suralimC) required by an engine control unit of said engine.

5. The method as claimed in claim 2, further comprising a step consisting of using the information about the value of the air pressure present in the air intake duct of the internal combustion engine provided by an air pressure sensor (PUT) arranged upstream of a butterfly valve for controlling the flow rate of air admitted into said engine, in order to verify if said set position (P.sub.c) corresponds to the supercharging pressure (P.sub.suralimC) required by an engine control unit of said engine.

6. The method as claimed in claim 3, further comprising a step consisting of using the information about the value of the air pressure present in the air intake duct of the internal combustion engine provided by an air pressure sensor (PUT) arranged upstream of a butterfly valve for controlling the flow rate of air admitted into said engine, in order to verify if said set position (P.sub.c) corresponds to the supercharging pressure (P.sub.suralimC) required by an engine control unit of said engine.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The only FIGURE shows a feedback diagram illustrating the implementation of an example of the method according to the invention for regulating the control of an electrical actuator of a wastegate arranged in the known manner in an exhaust circuit of an internal combustion engine of a vehicle, for example an automotive vehicle (not shown).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(2) The diagram of the only FIGURE defines the operation of a system for regulating the control of an electrical actuator 7 of a valve (not shown) permitting the exhaust gases of an internal combustion engine (not shown) to be diverted from the fluid supply circuit of a turbine of a turbocharger designed to compress the fresh gases admitted into the air intake circuit of the internal combustion engine. The electrical actuator 7 is controlled in the known manner by means of an H bridge (not shown) in order to permit a displacement of the valve in the direction of its closure and in the direction of its opening, according to which the current passes through the electrical actuator 7 in one direction or in the opposing direction. The system shown comprises two feedback loops 1, 2 as disclosed below.

(3) The set supercharging pressure P.sub.suralimC is present at the inlet 4 of the system, said set supercharging pressure being required in the known manner by the electronic control unit of the engine (not shown, hereinafter called ECU) as a function of a control of the engine torque on the part of the driver, and in particular further parameters of the heat engine, such as the speed, etc.

(4) The assembly consisting of the turbocharger and heat engine or internal combustion engine is present at the outlet 5 of the system, the turbocharger acting on the supercharging pressure of the heat engine.

(5) The signal of the measured supercharging pressure of the heat engine is provided by a PUT pressure sensor in the known manner, said sensor being arranged upstream of a butterfly valve for controlling the flow rate of air admitted into the heat engine. The signal of the measured supercharging pressure of the heat engine is advantageously used in the method shown, and permits in the known manner to form the first feedback loop 1 linking this pressure information with the inlet 4 of the system in order to monitor that the value of the supercharging pressure provided by the PUT sensor in a position reached by the valve, for example the set position P.sub.c as explained hereinafter, corresponds to the set supercharging pressure P.sub.suralimc required by the ECU as a result of a requirement for a given torque made by the driver of the vehicle by means of the accelerator pedal, for example. To this end, a regulator 12, for example a PID regulator as shown, is inserted into the loop 1 to regulate the supercharging pressure.

(6) In the known manner, a model 8 of the turbocharger and the wastegate permits, by estimation, an open position of the wastegate to correspond to a given supercharging pressure, for example a set open position P.sub.c of the wastegate for a set supercharging pressure P.sub.suralimc required by the ECU for a given engine, taking into account in particular the speed of the engine.

(7) The second feedback loop 2 is the loop which essentially implements an example of the method according to the invention and will now be described below by means of the only FIGURE. As shown in the FIGURE, a set position P.sub.c of the valve or wastegate is located at the inlet of the loop 2, originating from the outlet of the regulator 12 in the example, the outlet of the loop 2 being connected to the outlet 5 of the feedback loop 1.

(8) According to the method according to the invention, a first step (step 1), therefore, consists in determining a set position P.sub.c, for example a position estimated by means of a model 8 cited above which the valve has to reach from a known position P.sub.ref thereof. The current known position P.sub.ref of the valve is advantageously established from a known reference position of the ECU, for example by ascertaining the limits of displacement of the valve as will be explained below. This set position P.sub.c constitutes the inlet 13 of the feedback loop 2, as shown in the FIGURE. Moreover, an activation time of the electrical actuator 7 of the valve is defined as corresponding to a monitoring time t.sub.p thereof required to displace the valve to the set position P.sub.c by one displacement increment. The monitoring activation time t.sub.p defines the monitoring period of the loop 2 and is determined from the characterization of the system.

(9) According to the method according to the invention, a second step (step 2) consists in the information about the position P.sub.c which the valve has to reach being transmitted to an electronic control unit 6 of the electrical actuator 7 of the valve, in the example an electrical motor, via an H bridge (not shown) which activates the electrical motor so that the valve reaches the set position P.sub.c, to this end applying a control signal onto the actuator 7 until the set position P.sub.c is reached during an activation time, for example a multiple of the monitoring time t.sub.p. The electronic control unit 6 delivers in the known manner a control signal of the PWM type (Pulse Width Modulation). The valve or wastegate is, for example, a rotary valve (not shown) placed across an exhaust pipe (not shown) the rotary axle thereof being actuated by the electrical motor 7.

(10) According to the method according to the invention, a third step (step 3) consists in the electrical current i(t) which passes through the H bridge being measured during the monitoring time t.sub.p and a correction factor Km 9 being applied to the measured electrical current i(t) to obtain the motor torque Cm delivered by the electrical actuator during the monitoring time t.sub.p, according to the diagram of the loop 2 shown in the FIGURE. The correction factor Km may be obtained by calibration and is assigned to a given electrical actuator 7. This third measuring step 3 is preferably implemented by means of electronic components provided in the conventional manner on specific H bridges and controlled by the ECU.

(11) According to the method according to the invention, a fourth step (step 4) consists in the speed of displacement w(t) of the valve being obtained during the monitoring time t.sub.p, by the integration 10 of the motor torque Cm over the monitoring time t.sub.p, i.e. by the integration of the current i(t) over the monitoring time t.sub.p, as explained above and shown on the loop 2 in the FIGURE. This fourth step 4 may be obtained by means of an integrator placed, for example, in the ECU according to different integration methods of choice, for example the trapezoidal method, to be adapted as a function of the control signal of the actuator and, in particular, the sampling period of the PWM signal.

(12) According to the method according to the invention, a fifth step (step 5) consists in the position reached Pt.sub.p by the valve at the end of the monitoring time t.sub.p being obtained by the integration 11 of the speed w(t) of displacement of the valve over the monitoring time t.sub.p, as shown on the loop 2 in the FIGURE. In the same manner as the fourth step, this fifth step 5 may be obtained by means of an integrator positioned for example in the ECU, using for example the trapezoidal method.

(13) Once the position reached Pt.sub.p by the valve is known at the end of the monitoring time t.sub.p, a sixth step (step 6) of the method consists in comparing this position reached Pt.sub.p, with the set position P.sub.c. This sixth step 6 is, for example, implemented by means of a comparator integrated in the ECU.

(14) Subsequently, the method consists of a seventh step (step 7) to reiterate the steps 2 to 6 of the method, disclosed above, according to the feedback loop 2, until the valve reaches the set position P.sub.c.

(15) Advantageously, the displacement stops of the valve, in the extreme open and closed positions, are ascertained by means of a detector of current thresholds passing through the H Bridge, respectively for one direction of displacement and the opposing direction of displacement of the electrical actuator 7, in order to ascertain at least one initial reference position of the valve to establish the known position P.sub.ref thereof, for example that in which the valve is located at the moment where the ECU transmits the set position P.sub.c to be reached. The open or closed stop positions of the valve could be determined either by reading out the increase in current or by information obtained about the current limit reached. The information about the current limit reached is generally always integrated in the electronic components of an H bridge of the known type. These stop positions could advantageously serve to reset the parameters of the dual integration of the current/speed/position.

(16) In the supercharging operating zone imposed, namely in the intermediate position of the valve, i.e. in the activation zone for regulating the supercharging of the turbocharger, the pressure regulating loop 1 based on the measurement of the supercharging pressure by means of the PUT sensor will permit the position of the valve to be reset in order to establish the set supercharging pressure P.sub.suralimc.

(17) Preferably, an unwanted blockage of the valve between its extreme closed and open positions, the extreme open positions being excluded, will be detected by means of the detector of current thresholds passing through the H bridge which is used for ascertaining the positions of said extreme closed and open positions. This safety step will advantageously be integrated in the disclosed method in order, for example, to transmit a signal of the malfunction of the wastegate in the case of a blockage in its operating range between its extreme positions.