A MICROPROCESSOR-CONTROLLED DRIVE UNIT WITH LIMITATION OF CURRENT CONSUMPTION FOR ELECTRICALLY OPERATED DEVICES

Abstract: A drive unit for electrically operated doors, windows, screening devices and the like, comprises a drive unit casing (5) containing a motion transfer member (4) in engagement with a reversible drive motor (1) with an associated motor control circuit. The drive unit is designed as a program controlled unit with a microprocessor (6) with an associated memory in which as operating parameters for the drive motor (1) among other a predetermined maximum current supply is stored. The microprocessor is programmed for calculation of the current maximum current on the basis of the measured motor current and for initiating a reduction of the motor voltage and thus the motor speed, when the maximum current consumption is reached.

Description: A microprocessor-controlled drive unit with limitation of current consumption for electrically operated devices The present invention relates to a drive unit for electrically operated devices such as doors, windows, screening devices and the like, comprising a drive unit casing designed for stationary mounting and containing a motion transfer member designed for connection with the operated device and in engagement with a reversible drive motor with an associated motor control circuit which drive unit is designed as a program-controlled unit, the motor control circuit containing a microprocessor with associated memory with stored operating parameters. It is generally known, inter alia from US-A- 5,023,744, EP-A-0 544 132 and DE-A-37 15 244 to provide a usually thermal protection of the drive motor in drive units for electrically operated devices for the above purpose. With these known protective devices, the motor is usually disconnected in case of excess load. Such protective devices are, however, unsuitable for many purposes of use, as during a per se normal operation of a drive unit, momentary and rather heavy current increases can occur. This is e.g. the case with opening/closing drive units for doors and windows where during the last part of the closing movement a considerable seal pressure must often be overcome. DE-A1-42 34 501 relates to a motor control for door openers which are based on a redundancy concept with two independently working microprocessors which in two different ways calculate the driving torque of the motor. One microprocessor calculates the torque from the motor current supplied from an output stage . When exceeding a stored maximum torque, the motor is disconnected via a first disconnecting stage. The second processor calculates the torque from the motor characteristic and supplies data on load and revolutions per minute. Also in this processor the exceeding of a stored maximum torque will as a rule cause a disconnection of the motor via a second disconnecting stage. As an alternative to an actual disconnection of the motor, it is indicated that a current limitation circuit not further described can be activated for limitation of the motor current. Therefore, it is the object of the invention to provide a current consumption control for a drive unit of the stated type which is distinguished in that a momentary and heavy torque load of the motor can be handled without disconnecting the motor and without exceeding a predetermined maximum current consumption for the drive unit . These and other advantages are according to the invention obtained by a drive unit of the stated kind which is characterized in that the microprocessor is programmed for maintaining an essentially constant speed of the motor at varying loads, however, such that a predetermined maximum supply current for the drive unit is not exceeded, the stored operating parameters comprising said predetermined maximum supply current for the drive motor of the unit, that means for monitoring voltage and current to the motor are connected to the microprocessor, and that the microprocessor is programmed for calculation of the current maximum current consumption on the basis of the measured motor current and, when exceeding the stored maximum supply current, for initiating an adjustment of the motor voltage for reduction of the supply current to the stored maximum value . Advantageous embodiments for such a drive unit are stated in the subclaims. In the .following, the invention is explained more in detail with reference to the schematical drawing where Fig. 1 is a block diagram showing the principal components of an embodiment of a drive unit according to the invention and meant for the use as window drive unit, Fig. 2 shows the design of a circuit for limitation of the current consumption of the drive unit, Fig. 3 shows a graphic representation of the adjustment function, Fig. 4 shows the reprogramming of the drive unit by connection to a external programming device, and Fig. 5 shows the design of a circuit in the drive unit for the use by data exchange between the drive unit and the external programming device . The drive unit according to the invention is in the embodiment shown on the drawing designed as an self-contained, autonomous unit to be used e.g. in connection with a chain drive unit of the kind which is well-known for opening and closing of different window types, in particular roof windows. The drive unit comprises as principal components a reversible electrical drive motor 1 which via a built-in transmission 2 is connected to a drive member for the adjustment member of the drive unit, e.g. a chain wheel 3 which is in engagement with a chain 4 which at its one end is connected to a window frame whereas the motor 1, the transmission 2 and the chain wheel 3 together with the chain part 4 in engagement therewith and the electronic components in the drive unit are built into a casing 5 which is connected with the frame construction of the window. For the control of all operating functions, the drive unit contains a microprocessor 6 with control programs stored in an internal ROM. The microprocessor 6 is connected to a memory 7 which in the shown embodiment is constituted by a reprogrammable EEPROM 7 where the operating parameters of the function of the drive unit in the actual use are stored. The current supply to the drive unit is effected via two current supply conductors 8 and 9 which can be connected with an operation keyboard 10 and in the drive unit are connected to a voltage regulator 11 providing a supply voltage Vcc to the microprocessor 6 and other electronic components in the drive unit and furthermore via a direction interface circuit 12 and a data read-out circuit 13 are connected to the microprocessor 6. The current supply conductors 8 and 9 are furthermore connected to a motor driver circuit 14 controlled by the microprocessor 6 and controlling connection and disconnection together with the rotating direction of the motor 1. The microprocessor 6 can moreover be connected with an IR receiver 15 for the use in remote control of the drive unit from an IR remote control unit of a kind known per se. In the drive unit, the direction interface circuit 12 connected with the current supply conductors 8 and 9 contains, as shown in Fig. 5, two RC couplings 18 and 19 each in connection with one of the current supply conductors 8 and 9. The direction interface circuit 12 emits to two inputs 20 and 21 of the microprocessor 6 direction control signals which in the normal operating condition are unambiguously determined by the polarity of the current supply conductors 8 and 9 and determine the rotating direction of the motor 1. By way of example, if the current supply conductor 8 is positive compared to the current supply conductor 9, the capacitor in the RC coupling 18 is charged through the associated resistance, whereas the capacitor in the RC coupling 19 is discharged through the associated resistance whereby a direction control signal with the logical value "1" is emitted to the input 20, .whereas a direction control signal with logical value "0" is emitted to the input 21. If on the other hand, the current supply conductor 9 is positive compared to the current supply conductor 8, the direction control signals on the inputs 20 and 21 assume logical values "0" and "1", respectively. During normal operation, the microprocessor 6 controls the rotating direction for the motor 1 which is a DC motor, by activiation of the one of the two pairs of the field effect transistors 25, 26 or 27, 28 in the driver circuit 14 shown in Fig. 2, whereas the current and voltage to the motor are controlled by pulse width modulation in a PWM modulator 29 con- nected between the microprocessor 6 and the field effect transistors 25, 26 or 27, 28. The speed of the DC motor 1 determined by the motor voltage is monitored by the microprocessor by measurements of the motor voltage by means of a resistor network with resistances 30, 31, and 32 whereas the torque of the motor is monitored by voltage measurement via a current sensor resistance 33. In order to maintain the motor at a usually constant speed independently of the torque, the voltage measured by means of the resistor network 29- 31 is compensated for the voltage drop over the internal resistance of the motor calculated from the measured motor current . The current drawn from the current supply conductors 8 and 9 can thus be calculated by multiplication of the measured motor current by the duty cycle of the pulse width modulated signal. The program control in the microprocessor uses an adjustment algorithm which primarily tends to maintain a constant motor speed even though the motor is subjected to varying loads but such that a stored maximum current consumption is not exceeded. As long as the motor current or the current consumption has not reached the programmed maximum values, the following applies for the voltage V over the motor terminals where Ve is the EMF of the motor, Im is the motor current, Rm is the internal resistance of the motor and k a constant which for the stability is smaller than 1. When the current consumption or motor current reaches the programmed maximum, the motor voltage is reduced by control of the pulse width modulated signal, such that motor current decreases to programmed maximum whereby the motor speed is reduced. In the graphic representation in Fig. 3, the graph RPM shows the rotating speed of the motor, the graph Im the motor current, the graph 1st the current consumption and the graph "duty" the duty cycle of the pulse width modulated signal. Up to a torque load of 1.2 Nm the speed is maintained constant with increasing current consumption. The supply current is then limited to the maximum value stored in the memory 7 whereby the motor voltage and thus the speed are reduced. In order to be adaptable to changing needs and loads, the drive unit in the shown embodiment is designed for being reprogrammed through data exchange with an external programming unit which, as shown in Fig. 4, may be a portable PC 16 which via an interface unit 17 is connected to the current supply conductors 8 and 9 which in the operating condition are supplied with a DC voltage, e.g. a full-wave rectified supply voltage the polarity of which determines the rotating direction of the reversible motor 1 of the drive unit . In the . programming arrangement shown in Fig. 4, the interface unit 17 is adapted for switching the polarity of the current supply conductors 8 and 9 at a frequency which is considerably higher than the mains frequency, e.g. 10 kHz, whereby the drive unit as explained in the following is brought into a programming or data exchanging condition deviating from the normal operating condition. By the switching of the polarity of the current supply conductors 8 and 9 at a relatively high frequency which is effected in the programming and data exchange condition, the capacitors in both RC couplings 18 and 19 are discharged such that the signals emitted to the inputs 20 and 21 of the microprocessor both assume a low level corresponding to logical "0" whereby the microprocessor is brought into the programming or data exchange condition. Subsequent to the completion of the programming or data exhange and after the programming and interface units 16 and 17 are again disconnected, the microprocessor can only be brought back to normal operating condition by a separate reset operation, e.g. by giving an end command on the portable PC 16. In the programming or data exchange condition, there can by entering suitable commands on the portable PC 16 either be transferred data representing predetermined parameter values from this to the microprocessor 6 and the EEPROM 7 connected thereto or there can be read out stored data in the EEPROM 7 or the microprocessor 6 to the portable PC 16. The data transfer from the portable PC 16 to the microprocessor 6 can e.g. be effected in that the commands entered into the portable PC 16 in the interface unit 17 are converted into bit patterns transferred to the drive unit changing the polarity of the current supply conductors 8 and 9 by a suitably low frequency corresponding to a bit rate suitable for reception and decoding of the information. By way .of example, data can be transferred to the interface unit 17 by a standard NRZ bit coding from the serial port on the portable PC 16. A transmission of 300 baud corresponding to a maximum pulse rate of 150 Hz is thus obtained. The transferred bit patterns can thus be decoded by the RC couplings 18 and 19 and from there be delivered to the inputs 20 and 21 of the microprocessor 6 instead of the direction control signals supplied in the normal operating condition. In the microprocessor 6, a terminal 22 is connected to the EEPROM 7. The transmission protocol for transfer of parameter information from the portable PC 16 to the microprocessor 6 can be organized in frames or pages of each 8 bytes consisting of a serially transferred bit string of 8 bits. At the beginning of the transmission a byte is first transferred in the first frame with an instruction or command about started transmission followed by a byte identifying the parameter which is subsequently read and serves for addressing when reading in the EEPROM 7 and one or more control bytes . After a pause corresponding to the remaining duration of the first frame or page, the actual parameter information is transferred in the 8 bytes in the following frame upon which control frame ending information is transferred in the next frame. The transferred parameter data are buffered in a RAM in the microprocessor before being stored in the EEPROM 7 which e.g. can have a capacity of 16 frames or pages of 8 bytes or a total of 128 bytes. Programming and reprogramming of relevant operating parameters can thus be effected in connection with the production of drive units according to the invention and at later times, e.g. in connection with the end mounting. In connection with the production, the programming can typically comprise serial numbers and calibration constants together with certain function parameters, whereas in the end mounting it will typically be programming of operating parameters which can vary in dependence of the type of window, for which the drive unit is to be used and the working loads to which the drive unit can be expected to be subjected, and which typically can comprise maximum pull, speed or power or maximum opening degree for the window. A read-out data from the drive unit to the portable PC 16 can also be effected in the programming or data exchange condition, e.g. with the object of verifying the programmed operating parameters or reading out data which are logged in the drive unit . The data read-out is effected from the microprocessor 6 by connecting and disconnecting the load resistance 23 shown in Fig. 3 by means of a transistor switch 24 and in accordance with the bit pattern required to be read out. The thus caused changes in the current drawn by the drive unit from the current supply conductors 8 and 9 can in the interface unit 17 be registered and converted to a digital signal which after a suitable level conversion can be delivered to the serial port on the portable PC 16. The data read-out is effected by transfer of an instruction or command from the portable PC.

Claims: P A T E N T C L A I M S 1. A drive unit for electrically operated devices such as doors, windows, screening devices and the like, comprising a drive unit casing (5) designed for sta- tionary mounting and containing a motion transfer member (4) designed for connection with the operated device and in engagement with a reversible drive motor (1) with an associated motor control circuit which drive unit is designed as a program-controlled unit, the motor control circuit containing a microprocessor (6) with associated memory (7) with stored operating parameters (1) , c h a r a c t e r i z e d in that the microprocessor (6) is programmed for maintaining an essentially constant speed of the motor (1) at a varying loads, however, such that a predetermined maximum supply current for the drive unit is not exceeded, the stored operating parameters comprising said predetermined maximum supply current for the drive motor of the unit, and that means for monitoring voltage and current to the motor are connected to the microprocessor (6) , the microprocessor being programmed for calculation of the current maximum current on the basis of the measured motor current and, when exceeding the stored maximum supply current, for initiating an adjustment of the motor voltage for reduction of the supply current to the stored maximum value. 2. A drive unit according to claim 1, c h a r a c t e r i z e d in that the current and voltage to the motor (1) are controlled by pulse width modulation, and that the actual supply current is calculated by multiplication of the measured motor current by the duty cycle of the pulse width modulated signal. 3. A drive unit according to claim 2 , c h a r a c t e r i z e d in that the adjustment of the motor voltage is initiated by control of the pulse width modulated signal. 4. A drive unit according to claim 1, 2, or 3 , c h a r a c t e r i z e d in that the memory (7) is a reprogrammable memory in which the stored operating parameters, including said predetermined maximum supply current of the drive motor (1) in order to be adaptable to changing needs and loads can be programmed and reprogrammed from the outside via the current supply conductors (8, 9) to the drive unit by means of an external programming device (16) via an interface unit (17) which by connection to the current supply conductors (8, 9) brings these into a programming condition deviating from a normal operating condition and in which data can be exchanged between the microprocessor (6) and the external programming unit (16) . 5. A drive unit according to claim 4 where the rotating direction of the drive motor (1) in the normal operating condition is defined by the polarity of a DC voltage on the current supply conductors (8, 9), c h a r a c t e r i z e d in that the programming condition comprises switching the polarity of the current supply conductors (8, 9) at a frequency which is considerably higher than the supply voltage frequency . 6. A drive unit according to claim 5, c h a r a c t e r i z e d in that the microprocessor (6) is adapted for logging of data during operation of the drive unit and for in said programming condition to read out such data and/or stored operating parameters from the . reprogrammable memory (7) by microprocessor controlled connection and disconnection of a load resistor (23) connected to the current supply conduc- tors (8, 9) .

Inventors: DARUM JESPER, DARUM, JESPER
Applicants: DARUM JESPER, RASMUSSEN KANN IND AS, DARUM, JESPER, V. KANN RASMUSSEN INDUSTRI A/S
Application year: 1998
Main classification: H02P7
IPC codes: H02H7