DE19901840A1 - Electrical actuator for motor vehicle electric window, sliding roof or seat adjuster measures instantaneous rotation speed and/or torque and adjusts motor current accordingly - Google Patents

Abstract

A measuring device (1) is provided for determining the instantaneous value of the rotation speed and/or torque of the actuator. A current controller regulates the motor current based on the deviation of the instantaneous value from a control value. The control circuit is connected to a position sensor (8). The motor current controller uses a pulse width modulation in the range greater than 20 kHz. A method of controlling an actuator is also claimed.

Description

The invention relates to an electric actuator for motor vehicle components and a method for controlling it. Electric actuators are used in increasingly used for automotive components, especially as electric window regulator, sunroof adjuster and seat adjustment. Would be conceivable in the future also use z. B. in automatic door openers or the like. This Actuators are located in the vehicle interior, so that they run rough Actuators and the associated vehicle components in the vehicle interior is perceptible despite vibration damping means. The The running speed of these drives is clear between run-up and run-down different and thus audible and partly also visually perceptible. In addition Sluggishness significantly affect the running of the disc, which is clearly reflected in maps the disk speed.

The control of the actuators is jammed in newer systems Protection on how it can be found, for example, in DE 44 20 359. To avoid Injuries are the maximum values of the drive torque predefined and defined at which pinching torque the motor should switch off. This is usually done by means of current monitoring, which occurs when an over current switches off the motor or in the opposite direction controls. The torques or currents required to start the actuator However, they are generally very high, for example for magnetizing the rotor that when switching on very difficult between a high inrush current or an overcurrent caused by pinching can be distinguished and consequently, this area is generally hidden for the anti-trap protection. The actuators are usually switched off by overcurrent detection Contactor at the end positions or, for example, period duration comparison, with long periods a slow motor and high torque mean. Tolerances for mechanical components or electrical ones  Operating variables, external influences, such as the temperature, for example when freezing the Disc, lead to greatly changing running characteristics, a slowdown or a restless run.

The object of the invention is an actuator and a control method specify by means of which an adaptation to the current operating conditions possible and a compensation of deviations is possible. This task is accomplished by the Main claims 1 and 7 solved. Advantageous further developments are the sub claims.

The method has a speed and / or torque controlled operation. Accordingly, the device for controlling the actuator has one Device for recording the actual speed and / or a device for recording of the actual torque as well as a current control, which the motor current in Dependence on the deviations from the target speed and / or target torque regulates. The current control for influencing the motor current can be technical be designed differently. A corresponding one is preferably used Pulse width modulated voltage signal supplied. The pulse ratio will adjusted accordingly as soon as, for example, the actual speed of one specified target speed deviates. The speed control is preferably the Torque control is subordinate to the pulse ratio until it is reached controls a required torque change and the pulse ratio is subsequently corrected according to the speed control. The speed Torque control also allows active control of engine operation in all four quadrants of the speed-torque map, including that active braking by means of a counter directed against the current speed Torque or holding torque at zero speed. The Torque detection and control is preferably carried out by the motor current as an electrical parameter proportional to the torque.

By detecting the motor current, the actuator can also be blocked or the associated vehicle components recognized early on that maximum torque limited by the control or at a corresponding Power increase can be switched off early. In particular, the limitation to one certain maximum torque is to meet the safety requirements Specifications in the automotive field of particular importance. While Switch off conventional systems when the maximum torque is reached must be kept and controlled with a torque control become. Especially the starting torque can be limited and e.g. B. ramped  can be increased, whereby the drive can be gently started. Then only the specified starting torque occurs and thus a definable one maximum force, which also protects the mechanics. The engine is running slower, but does not generate impermissible torques or Clamping forces more.

It can also be switched off by coupling with a position counter be reached when an end position is reached, so that it does not have to in these cases a large current rise due to the blocking, or position-dependent, the speed and or the torque specified and be regulated accordingly. Especially when it comes to the risk of getting caught Specification of a torque characteristic or different depending on the position Target torques advantageous because in non-safety-critical areas of the Adjustment path higher torques can be specified in the trapping however, the danger zone is lower.

In the prior art, gears are used which have a very high self-locking have to the actuator at rest in a desired position hold. However, the self-locking reduces the efficiency. One uses an actuator with speed and torque control, so the speed kept at zero and a holding torque counteracting changes in movement are generated, for example in the event of an attempted downward movement of a Pulley of an electric window regulator the pulse width modulated are energized in such a way that the disc cannot move or this is counteracted.

When the predetermined position is reached, an energy-saving stand-by operation of the actuator can be assumed, in which, for example, the actuator itself is no longer energized, the actuator being reactivated on the basis of an actual speed of the speed measuring device ( 1 ) that deviates from zero.

The invention is described below using exemplary embodiments and figures explained in more detail.

Brief description of the figures;

Fig. 1 diagram of the speed and torque control for an actuator,

Fig. 2 actual torque measured in terms of motor current and position dependent definition of the reference values,

Fig. 3 current waveform in a case of trapping,

Fig. 4 current flow during brief load surges in the clamping portion without Einklemmschutzreaktion,

Fig. 5 current curve and target torque matching at a mechanical fault in the actuator,

Fig. 6a, b change in position and speed curve at controlled and uncontrolled operation,

Fig. 7 circuit diagram of an actuator with a control circuit,

Fig. 8a, b delineation of the pulse width modulated control of the switching means and current flow in dependence on the pulse ratio.

Fig. 1 shows a diagram of the speed-torque control circuit for an actuating drive, consisting of a motor M, a speed measuring device 1, a microcontroller 2 for the control, an internal control circuit 3 with the rotational torque control 4 and the current controller 5, an outer control loop with a speed control 6 , a current setpoint limitation 7 and a position detection 8 .

Output of the control is reached by the motor M actual rotational speed _n, which is detected by the speed measuring device 1, for example a non-contact Hall sensor and converted into an electrical signal. The torque is recorded in the form of the actual current I _ist proportional thereto, for example via a shunt resistor (not shown). The entire control can take place in the form of separate components or in an appropriately programmed micro controller 2 . The scheme of control consists of an outer control loop with the actual speed _{n to} n as the controlled variable and the target rotational speed (x) as a reference variable. _To the target speed n (x) is in this case depending on the position set in this embodiment of the position sensing. 8 The speed controller 6 acts as a control device, which determines a correction torque in the form of a target current isoll1 as a manipulated variable in accordance with the deviation between the actual and target speed. This setpoint current isoll1 is compared in a current setpoint limitation 7 with a maximum current i _max (x) likewise determined by the position detection 8 as a function of the current position x, and a setpoint current isoll2, which may be reduced, is determined. This limitation is necessary in order to avoid incorrect control when pinching, because the speed will first decrease or not be reached and the speed control will specify a correspondingly high target current. But since there is a pinch, e.g. B. in the pinching area of a car window, there is a limitation by the current setpoint limit 7 , which can be controlled by position detection 8 position-related.

The inner control circuit 3 consists of the actual torque in the form of the actual current i _is as a control variable and the correction torque of the outer control circuit in the form of the target current i _soll2 as a _reference variable, the torque control 4 as a control device and the pulse ratio as a manipulated variable that corresponding to the deviation of actual and desired torque or the setpoint and actual current i _{soll2 -i} is changed, and the driven from the above, the controller 5 and the switching means actuator in the control system, wherein through the controller 5 medium that or the switching according to the variable Pulse ratio can be controlled as a manipulated variable. The inner control loop 3 has a time delay τ1 determined only by the electrical quantities of inductance and resistance of the motor, so that this inner control loop 3 can be adapted very quickly. In contrast, the outer control loop has a significantly larger time delay τ2, which is due in particular to the transformation of electrical into mechanical energy, until a corresponding increase in speed is brought about from a current increase. In addition to the moment of inertia of the moving system, i.e. the rotor, the gearbox and the motor vehicle comfort element moved by it, e.g. the window pane or the sunroof, the external load moments, such as friction, in particular also local stiffness etc., flow into the outer control loop. Adjusting the manipulated variable too quickly would also lead to instability in the control loop.

Fig. 2 shows an example of a closing process of a window pane, the controlled course of the motor current I over time t or position x. If the motor is energized in the idle state at time t0, the actual current I could initially only increase sharply due to the internal resistance of the windings and generate an impermissibly high starting torque. On the other hand, a higher torque is required for overcoming the idle state and static friction than for moving an already moving disc. Accordingly, the current maximum is kept relatively high for a first time range up to t1, the actual current being correspondingly limited accordingly by pulse-width-modulated control of the switching means. If the motor first overcomes the inertia of the rotor, there is a sharp drop in torque until the normal load torque consisting of the inertia of the moving parts and the friction is reached after overcoming the play of the mechanical components due to manufacturing tolerances. For example, the target torque or, analogously, the maximum current I _max (x) can be adjusted in a step-like manner, an average value being maintained until t2. On the one hand, a window pane moves part of the way concealed within the door, on the other hand, the sizes of objects that are particularly vulnerable to jamming, such as the arm or head, are often significantly smaller than the total path of the pane, so that there is definitely no risk of being jammed in part of the adjustment path. In the path area at risk of pinching, which was outlined on the basis of the disk ramp-up in FIG. 2a, that is to say from t2, for example in the upper third of a disk path, the target torque is reduced to the lowest value I _max 0, which as the maximum permissible value in the vehicle comfort area during pinching z . B. is given according to various guidelines f ← 100N at a spring rate of 10 N / mm. This control is particularly advantageous for hard pinching bodies (e.g. 65 N / mm) because the current control responds very quickly. Previous systems have always had great difficulties in this area. This control of the actuator can also significantly reduce the torques or clamping forces if necessary. Since the actuator in this area has already reached a rotational speed that can possibly be maintained even with very low drive torques, a very high level of security against jamming can be achieved here.

If the disk reaches the upper end area from t3, the maximum current becomes again increased to close the disc with the rubber-like sealing lip to reach. However, the engine comes to a stop and rises with decreasing If the speed of the current is now extremely high, the current is already attacking limitation and reduces the maximum contact torque. Of course the torque can be brought to zero early on or as a braking torque negative value can be regulated before blocking occurs.

In contrast, FIG. 3 shows a simulated disk run-up, in which pinching occurs from t5. It can be clearly seen that the motor current I initially remains limited to the low maximum current I _max 0 by adapting the pulse ratio accordingly. The pinching force therefore remains limited to the maximum torque _value corresponding to I _max 0, for example 50 N. Is this maximum current permanently for a certain time, the period of time, for example, free of z. B. 0 ms to 100 ms can be determined, the motor is switched off at t6. In principle, of course, current can subsequently also be supplied in the opposite direction of rotation, but this was not shown in FIG. 3. In principle, a threshold would also be conceivable, which increases continuously up to a maximum value if there are doubts about trapping for any reason, and then switches off.

In Fig. 4 it can be seen in comparison that very short disturbances in t7, for example due to shocks due to the time delay of the control loops, there is no reaction or there is a corresponding current and thus torque limitation without immediate shutdown. This also means that the maximum values of the current or torque can be set lower than in conventional actuators with pinch detection and immediate shutdown when the current threshold is exceeded, since holding a maximum torque or current for a time, as in FIG. 3, between t5 and t6, is not possible. As a result, the maximum thresholds must be set to higher values at the expense of safety, in which short disturbances have little influence.

In contrast, FIG. 5 shows yet another variant of how to deal with disturbances in the current and therefore torque curve. In FIG. 5, the first time I _max 0 is exceeded for a short period to t8. Thereupon the control can also react by the maximum current threshold slightly, e.g. B. is also continuously raised. E.g. the shape and rate of increase of the disturbance can also be assessed. It is therefore possible to provide a very early responding lower maximum current threshold and a higher upper maximum current threshold, several thresholds or a continuous adjustment, the lower maximum current threshold being used, for example, to overcome stiffness and to maintain the motor movement at a certain speed. If the maximum current threshold is then raised when the lower one is reached, it can be observed how the motor current reacts to it. If it drops immediately or after a short climb, it is most likely a stiffness or a bumpy bump that has been overcome. In the event of a trap, however, the torque and thus the current will increase to the current maximum current value and remain there. Additional information can thus be obtained from the reaction of the motor current to an adaptation of the maximum current threshold. If local stiffness was involved, a correspondingly adapted maximum current value curve can be specified during the next start-up by coupling with the position detection, i.e. between t8 and t10, for example, the maximum current is saved as the maximum current and then automatically preset. It is only a question of the memory requirement, for which and how large path sections different target speeds and / or target torques are specified.

FIGS. 6a and b show the change in position x (t) and speed curve n (t) at controlled mode (f1) and an unregulated mode (f2) of an actuator to the beneficial effects of the speed and / or torque control, in particular on motor vehicle comfort components clarify. Ideally, an almost linear change in position x (t) (cf. FIG. 6a) can be achieved by the controlled operation. In contrast, the uncontrolled operation with conventional actuators shows strong irregularities. This can also be understood very well on the basis of the speed curve n (t) according to FIG. 6b. Ideally, a trapezoidal course with an acceleration and deceleration ramp is shown. Relatively constant speed and a linear change in position are particularly important in the automotive comfort sector, since the comfort components in particular have an aesthetic aspect and therefore smooth running and low noise levels will be of particular interest in the future. Especially with today's window regulators, the difference between up and down is clearly audible. By regulating the speed and torque, uneven running can be compensated and unpleasant running noises can be avoided, such as a significant drop in speed due to stiffness and subsequent re-acceleration. In addition, operating voltage fluctuations can be compensated for in a wide range, for example, if the motor is designed for 8 V, the board voltage could e.g. B. fluctuate in the range of 9-15 V without this affecting the speed, since this can be corrected by the controller.

Fig. 7 are a circuit diagram of a winding terminal of the motor M is an actuator with a control circuit for controlling the motor M by means of a so-called H-bridge consisting of two electronic switching means provided on both sides S1. . . S4, which are controlled by a control circuit 5 pulse-width modulated with a pulse frequency with inaudible range, for example at 20 kHz. The switching means S1 and S2 can alternately connect the motor M with an operating voltage UB, the switching means S3 and S4 each with a direction reference potential (ground ┴) connecting point, with either the switching means S1 and S4 or S2 for energizing the motor and S3 are closed, the current direction indicating the desired direction of rotation. If the current supply is switched off or reversed, the time lag in the old direction of rotation is limited due to the inertia at which a generator voltage is induced. To switch off, the motor M can therefore be short-circuited via the switching means S3 and S4 or one of the inherent diodes DI.

The internal structure of the switching means S1 to S4 is shown in FIG. 7a and instead a functional symbol is outlined in FIG. 7, since the configuration of these electronic switching means is of course variable. The particular advantage of using a MOSFET according to FIG. 7a lies in addition to the low forward resistance and the de-energized control voltage in that a simple substrate connection to the source results in an inherent diode DI, which is important for the tracking detection not described in this application and which relates to the operating voltage UB and Reference potential ┴ is polarized in the reverse direction, but a generator voltage polarized for this purpose for one diode in each case in the forward direction arises during overrun.

The resistor R, which is arranged between the connection point of the switching means S3 and S4 and the reference potential (ground ┴), is used for current measurement and thus as an actual torque measuring device. The voltage drop occurring above this is fed to the torque control 4 .

The motor current I is also detected in a direction-related manner, for example by providing a shunt resistor Rs between the actuator and switching means, the direction of rotation being derived from the current direction in the position detection 8 . The position detection 8 is also connected to the speed sensor 1 which, in analogy to FIG. 1, detects the actual speed nact. The position detection 8 can derive the position from the speed and direction of rotation and use it for a position-dependent specification of the desired speed and the desired torque. For this purpose, the microcontroller .mu.C, which contains the functions of speed control 6 and current limitation 7 , is provided with position x in addition to the set speed and the current set current isoll is derived as a quantity proportional to the torque.

This target current is fed to the current control 4 , which derives the required pulse ratio for the pulse-width-modulated control of the switching means from the actual current and the target current and transfers it to the control 5 of the switching means S1 to S4, which controls this switching means accordingly. The current control 4 and the control 5 of the switching means can be connected to the microcontroller μC via connecting lines or the functions of the elements 4 , 5 , 6 , 7 can be included therein. The clocking of the elements according to the pulse frequency can then take place via the microcontroller clock.

Fig. 8a and b shows the puslweitenmodulierte controlling the switching means, in which case the control signal 4 is shown .S the current control. The pulse ratio T1 / T2 can be adjusted depending on the required speed and / or torque correction. During T1 are controlled switch means in a rotation direction and T2 in the other rotational direction at a H-bridge circuit according to Fig. 7, so that no torque is formed with a pulse ratio of 50% as based on the current in Fig. 8b detected can. In this case the current fluctuates around the zero position. If the pulse ratio is changed by T1 <T2, the current increases on average, when T1 <T2 it decreases to negative. Accordingly, a positive or negative torque would arise and the motor would change its speed or direction of rotation in addition to the torque.

Claims (16)

1. Electric actuator (M) for motor vehicle comfort components, in particular electric window lifters, sunroof adjusters and seat adjustments, in a motor current-carrying circuit, characterized in that a speed and / or torque measuring device ( 1 , R) for detecting the actual speed and / or the actual torque (n _ist , i _ist ) of the actuator and a current control is provided, which the motor current depending on the deviations of the actual speed and / or the actual torque (n _ist , i _ist ) from predetermined setpoints (n _should , i _should ) regulates. 2. Electric actuator according to claim 1, characterized in that the control circuit is connected to a position counter ( 8 ) which is connected to the actual speed measuring device ( 1 ) and starting from a defined starting position and the actual speed (n _is ) the current position (x) determined,
_(to n (x), i _to (x)) different in the control circuit in dependence on the position (x) and / or the direction of movement set values of the rotational speed and / or torque are stored and the control circuit the actual speed and / or the actual torque _{(n, i)} ent _(to n (x), i _to (x)) speaking these setpoints controls depending on the current position (x) and / or direction of movement. 3. Electric actuator according to one of the preceding claims, characterized in that the speed control is provided as an outer control loop (τ2), which is subordinate to the torque control as an inner control loop (τ1) by

• a of the outer control loop) consists of the actual speed (n _ist) as the controlled variable and the target rotational speed (n) _{is intended} as a reference variable, the speed control device as a control and a correction torque (i) _to as a manipulated variable, which according to the deviation between actual and desired speed (n _soll) is determined,
• b) the inner control loop consists of the actual torque (i _ist ) as the control variable and the correction torque (i _soll ) of the outer control loop as the reference variable, the torque control ( 4 ) as the control device and the pulse ratio (T1 / T2) as the control variable, that according to the deviation of the actual and target torque is changed, and the actuator (M) controlled by the switching means ( 5 , S1, S2, S3, S4) in the controlled system, the switching means ( 5 , S1, S2, S3, S4) is controlled as a manipulated variable in accordance with the variable pulse ratio (T1 / T2).

4. Electric actuator one of the preceding claims, characterized characterized in that the current control of the motor current modulates pulse width with a pulse frequency in the inaudible range, preferably greater than 20 kHz, by at least one electronic switching means (S1, S2, S3, S4) in the Load circuit takes place, which ent with one of the deviation counteracting pulse ratio (T1 / T2) can be controlled. 5. Electric actuator according to one of the preceding claims, characterized characterized in that at least one shunt resistor (R, RS) is provided which detects the motor current flowing through the actuator (M) and the Control circuit is supplied as a torque-dependent variable. 6. Electric actuator according to one of the preceding claims, characterized in that at least one sensor is preferably provided as a Hall sensor as a speed measuring device ( 1 ), the signal of which is fed at least to the control circuit, preferably also to the position counter ( 8 ). 7. The method for controlling an electric actuator of motor vehicle comfort components according to one of the preceding claims, wherein the actual speed and or the torque proportional to the actual current (n _ist , i _ist ) of the actuator automatically by means of the pulse ratio (T1 / T2) to a predetermined target speed and / or a target current _(to n, i _soll) is regulated. 8. The method of claim 6, wherein the speed regulation is subordinated to a torque control by the speed control (6) a required for the correction of deviations of the actual speed from the predetermined target rotational speed nominal current (i _soll) determined and this desired current (i _soll) of the torque control (4) feeds, which changes the pulse ratio of the switching means in accordance with, until it reaches first the required nominal current (i _soll) and subsequently the now rising on the target rotational speed actual speed _(i) results in a recycling of the torque. 9. The method according to any one of claims 7 to 9, in which the current position (x) is derived starting from an initial position and the actual speed (n _ist). 10. The method of claim 9, wherein in dependence on the current position (x) target rotational speed and / or setpoint current (n _set (x), i _to (x)) are adapted. 11. The method of claim 10, wherein the actual speed (n _ist) is initially approximately linearly controlled to a target speed within a predetermined first section of line segment within a predefined second stretching is maintained constant and regulated in a third track section approximately linearly to zero . 12. The method according to claim 11, wherein a further route section is provided, in particular in which there is a risk of being caught, in which the target speed compared to that in the second section is lower. 13. The method of claim 10, wherein the actual current (i _ist ,) is limited to a first maximum value in a first route section (t0-t1) and limited to a second maximum value in a second route section (t1-t2). 14. The method according to any one of claims 7 to 12, in which from the duration (t5-t6) of the presence of a motor current exceeding a predetermined maximum value (i _max 0) of the current, a blocking of the actuator and the vehicle components connected therewith is detected. 5. The method according to claim 7, wherein the actuator (M) is automatically held in a predeterminable position by the set a target speed of zero and by means of the pulse ratio (T1 / T2) the actual current (i _ist ) is controlled so that a Movement changes counteracting holding torque is generated. 16. The method according to claim 15, in which when the predetermined position is reached, an energy-saving stand-by operation of the actuator is assumed and the actuator is reactivated on the basis of a non-zero actual speed on the speed measuring device ( 1 ).