MXPA96005460A

MXPA96005460A - Engine controller for electronically switched cd engines, to compensate for torque drops

Info

Publication number: MXPA96005460A
Application number: MXPA/A/1996/005460A
Authority: MX
Inventors: Link Hermann; Gleim Gunter
Original assignee: Deutsche Thomsonbrandt Gmbh
Priority date: 1995-11-10
Filing date: 1996-11-08
Publication date: 1997-08-01

Abstract

In an engine controller for electronically switching CD engines, an additional current and/or voltage is applied upon switching in the direction of the engine coiling system which is active, to prevent torque drops. To compensate for torque drops at different engine loads, the length of said additional current and/or voltage and/or amplitude are determined from the engine actual load.

Description

ENGINE CONTROLLER FOR ELECTRONICALLY SWITCHED CD ENGINES TO COMPENSATE TORQUE FALLS DESCRIPTION OF THE INVENTION The present invention relates to a motor controller having electronic switching which is connected to the coils of a motor, a predetermined additional current being connected to that coil of the motor which is active at that moment, from the instant of switching , to avoid the falls of the torque. US Pat. No. 4,511,827 discloses a controller that drives an electronically commutated motor so that torque fluctuations are suppressed. This device in this case comprises a sensor for determining the position of the rotor, in other words at the time of switching and a controller that processes this signal so that it is fed to the corresponding coil, from the moment of commutation, with an additional current for avoid falling torque, However, it has been found in the case of the known solution that the supply of a predetermined current to the coil only compensates for the drops of torque within a specific motor current range. However, for example in a video recorder, the known method does not provide satisfactory results since in the operation mode (for example exhibition and prolonged display), the currents can be extremely different due to different mechanical loading, for example in the case of different temperatures or cassettes. The invention is therefore based on the object of providing a motor controller in which torque drops are avoided even in the case of different motor loads. The object of the present invention is achieved by means of the features of claim 1. Preferred embodiments of the invention are specified in the consecutive claims. In accordance with the invention, in the case of a motor controller for electronically commutated DC motors, in which an additional current is connected to the active coil, from the moment of commutation, to prevent the falls of torque, the duration and / or pulse amplitude of the additional current is determined as a function of the motor load. In other words, the duration and / or amplitude of the additional current pulse is variable and is derived from the motor load, with the pulse of the additional current being longer (higher) while the motor load is higher, which is evident .

This results conveniently in the compensation of automatic torque drops and optimally, independently of the dispersion of production between engines, the ranges of temperature and aging. The motor controller according to the present invention normally controls the motor by means of the so-called pulse width modulation (CP M or PWM) of the control pulses. The PWM signal of the motor controller is maintained at "1" for the duration of the additional current. The switching instant, from which the additional current is applied, can be determined by a sensor. The load of the motor is determined from the motor current obtained, it being possible to determine the motor current, for example, by means of a measuring resistor which is connected in the motor circuit or from the ratio of the duration of the motor. pulse with the pulse pause of the PWM signal. In addition, the controller according to the invention can have an integrator that produces a control signal (S) from the working relationship of the CPWM signal. The start of the integration of the CPWM control signals is achieved in the same way by the occurrence of the switching signal.

The controller advantageously has a tilting whose output Q is connected to the control signals CPWM by means of an "OR" gate, so that the Q output is connected to logic "1" at the occurrence of the switching signal, the Q output of the jogger being readjusted when the control signal corresponds to a reference voltage. This comparison between the reference voltage and the control signal is preferably carried out by means of a differential amplifier. This thus achieves the end of the integration of the CPWM signals. A preferred embodiment of the invention will be explained in the following text with reference to the figures, in which: Figure 1 shows a circuit diagram of the compensation section, according to the invention, of the motor controller. Figures 2a and 2b show tuning diagrams of the input and output signals required for control purposes, and Figures 3a and 3b show the waveform of the current in an electronically commutated motor, respectively without and with compensation. Figure 1 shows the logic circuit to compensate for torque drops in electronically commutated digital drive motors. A digital motor control signal CPWM, in which the load of the motor can be derived from the working ratio, is passed to the compensation circuit input 1. A control signal S is derived from this signal CPWM by means of a integrator 2. The integrator 2 preferably comprises three series resistors R ^ R2 and R3, as well as two capacitors C- and C2, being C-, electrically arranged between the ground (reference earth potential) and the junction of R- ^ and R2, and C2 being electrically arranged between the ground and the junction of R2 and R3, and the control signal S being formed in C2. The control signal CPWM for controlling the motor, which is not illustrated, is passed in addition to an input of a composite OR 3, so that a PWM control signal appears at the output of the OR 3 gate and is supplied to the stages of PWM power, which are also not illustrated to provide the motor current in the coils or windings of the individual motor. The control signal S that is produced by the integrator 2 is supplied to the inverting input of a differential amplifier which is designed as a comparator 4 and in which a reference voltage UREF is applied, which is defined by means of a voltage divider composed of resistors R4, R5. The output of the comparator 4 is passed to the reset input of a flip-flop 5, which is formed by a flip-flop D. The input D of the flip-flop 5 is a positive potential that can be derived, for example, from a working voltage U ^ . The occurrence of the switching signal I for the motor driver activates the jogger 5 by means of the clock input, so that a logic "1" appears at the output Q. The output Q of the jogger 5 is passed to the other gate input OR 3. As a result of the CPWM signal being linked to the Q output by means of this OR circuit, the PWM signal for the power stages is consequently maintained in logic "1" or in the level " high ", so that an additional current is supplied to the motor winding. The output Q of the jogger 5 remains in the logic "1" until the logic "1" appears at the output of the comparator 4, so that the jogger is readjusted by means of the input R of readjustment of the jogger 5 and, consequently , a logic "0" appears in the Q output or the Q output remains in the "low" level. An npn transistor T is connected between the reversing input of the comparator 4 (control signal S) and the output Q of the tilter 5, so that the base is connected to the output Q by means of a resistor R6. The transistor emitter T which is at a positive potential of the operating voltage U ^ is connected to the base by means of a resistor R7, while the collector of the transistor T is connected to the reversing input of the comparator 4. When the output Q of jogger 5 changes to logic "1" transistor T is switched off, while logic "0" on output Q of jogger 5 opens transistor T or connects it. The transistor T acts therefore as an electronic switch by means of which the capacitor C2 in which the signal S is formed can be charged to a positive potential of the operating voltage U ^ depending on the condition of the logic signal in the output Q of jogger 5, or, when output Q is connected to logic "0" or to the "low" level, it can be discharged to the potential resulting in capacitor C- ^ as a result of the continuous integration of the CPWM signals which they are supplied continuously by means of the resistor R-j_. The discharge time constant of the capacitor C2 in this case is determined in particular by the parallel circuit formed by the resistor R3 and the resistor R2, the latter forming a circuit in series with the capacitor C-L to discharge. The charging time constant of capacitor C2 is determined by the resistance of the emitter-collector on course through transistor T. Figures 2a and 2b show the waveform of the various control signals with respect to time, the Figure 2a illustrates the case when the load of the motor is low and Figure 2b illustrates the case when the load of the motor is high. The waveform of the upper clock in Figure 2a shows the motor control signal CPWM, the working ratio being relatively low. When the switching signal 1 occurs, the output Q of the flip-flop 5 is connected to the "high" level, so that the transistor T is switched off and defines the start of the production of the control signal S. This means that the voltage on the capacitor C2, which corresponds to the control signal S, it drops accordingly until the jogger 5 is reset by means of the input R. This results in the low clock waveform at the output of the gate OR 3 ie the output of the gate OR 3 the logic "1" for the duration of the current control signal S which means a positive potential with respect to the reference earth potential in the present case, while logic "0" is, for example, the ground potential reference. Figure 2b shows the same situation as theFigure 2a, but with the control signal of the CPWM motor having a greater working relationship. As a result of the higher duty ratio of the CPWM motor control signal, the capacitor C ^ _ is charged at a higher voltage compared to the situation in accordance with FIG. 2a. The consequence of this is that the capacitor C2 is discharged more slowly and the waveform of the current control signal S also lasts a longer time, so that the period of time for which the output of the OR gate 3 remains in logic "1" is significantly longer. Figure 3a shows the current waveform in one of the motor windings without compensation in accordance with the invention for the falls of the torque. The upper part illustrates the switching instants. The lower part shows the waveform of the current as a function of time. It can be clearly seen that the drop occurs in the current waveform and therefore in the waveform of the torque of a motor at the switching instants. In contrast to this, Figure 3b shows the current waveform in one of the motor windings where current and / or voltage compensation is used to prevent torque drops. The current waveform and therefore the waveform of the motor torque is approximately constant at the switching times.

Claims

1. A motor controller for electronically switching DC motors, in which an additional current and / or voltage is connected to the active motor winding from the moment of commutation to avoid the falls of the torque, characterized in that the duration and / or amplitude The current pulse and / or additional voltage is derived from the motor load.

2. The motor controller according to claim 1, characterized in that the motor is driven by a pulse width modulation (PWM). The motor controller according to claim 2, characterized in that the PWM signal is maintained at logic "1" for the duration of the current and / or additional voltage. The motor controller according to one of the preceding claims, characterized in that the switching time is determined by a sensor. The motor controller according to one of the preceding claims, characterized in that the motor load is determined by the motor current obtained. 6. The motor controller according to claim 5, characterized in that the motor current is determined by a measuring resistor in the motor circuit. The motor controller according to claim 4, characterized in that the motor current is determined by the ratio of the duration of the pulse to the pulse pause in the PWM signal and / or from the speed of rotation of the motor. The motor controller according to claim 7, characterized in that the controller has an integrator that produces a control signal (S) from the working relationship of the PWM signal. The motor controller according to claim 8, characterized in that the controller further has a rocker whose output Q together with the control signal PWM form the inputs of an OR gate, so that the Q output is connected to the logic "1" at the arrival of the switching signal (I), and the Q output is reset when the control signal (S) corresponds to a reference voltage (UREF). 10. The motor controller according to claim 9, characterized in that the comparison between the reference voltage (UREF) and the control signal (S) is carried out by means of a differential amplifier. SUMMARY In the case of a motor controller for electronically switching DC motors, an additional current and / or voltage is passed at the instant of commutation to the winding of the motor that is active at the time, to avoid the falls of the torque. To compensate for the drops in torque at different motor loads, the duration and / or amplitude of the additional current and / or voltage is determined from the actual load of the motor. [Figure 1] List of reference symbols 1 Compensation circuit 2 Integrator 3"OR" Gate 4 Comparator 5 T Jogger Transistor Rl Resistor R2 Resistor R3 Resistor R4 Resistor R5 Resistor R6 Resistor R7 Resistor Cl Capacitor 2 Capacitor S Control signal I Switching signal CPWM - Motor control signals UREF "Reference voltage OUT - Jogger output PWM - Motor control signal