Electricity: motor control systems – Closed loop speed control system for dc motor with commutator – Armature control by digital or combined analog and digital...
Patent
1998-06-02
2000-07-18
Martin, David
Electricity: motor control systems
Closed loop speed control system for dc motor with commutator
Armature control by digital or combined analog and digital...
388819, 318599, 702 79, H02P 517
Patent
active
06091887&
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method of controlling a physical parameter, in particular the rotation speed of a motor, and an arrangement for carrying out such a method.
1. Background
Such a method and a practically tried arrangement is known from DE 44 41 372 A1, JESKE et al., corresponding to U.S. Ser. No. 08/341,380, now U.S. Pat. No. 5,845,045, issued Dec. 1, 1998.
This known method, however, is difficult to apply to different types of motors, since the program has to be changed in most cases.
2. Summary of the Invention
It is an object of the invention to provide a new method of this type, as well as an arrangement for carrying out such a method.
According to the invention, this object is solved by a method of controlling the actual value of a physical quantity, to a predetermined value, in the following called "target value", comprising the following steps: following referred to as "control deviation", and its sign, in the following referred to as "control sign", are determined repetitively at certain time intervals; into at least one electrical signal, the duration of the electrical signal, in the following referred to as "control deviation duration", being proportional to the absolute value of the control deviation, at least in the range of the target value, and the value of the electrical signal being a function of the control sign; deviation duration, the charge of an analog electrical memory arrangement is influenced; physical quantity is directly or in directly influenced, so as to keep it in the range of the target value.
This allows a precise and rapid control which is easy to implement. Advantageously, a part of this control arrangement can be realized with an inexpensive microprocessor while another part can be realized by using simple analog components. The resulting costs are low and the control process is very fast and accurate and can be adapted to different control tasks by simply changing the analog section.
In another advantageous embodiment of the invention, in step b) the control deviation is converted into an electrical signal in a microprocessor and this signal is outputted at at least one output of the microprocessor in the form of a binary or ternary signal which is generated in the microprocessor, during or after a measurement during the control deviation duration. This can be accomplished by an inexpensive microprocessor with a small word length, for example 4 bits. The microprocessor can also be used with an electronically commutated motor (ECM) to control the commutation.
In another advantageous embodiment of the invention, in step c) a capacitor operating as an analog memory means can be charged or discharged via an arrangement of resistors, with a current flowing through the resistors to or from the capacitor during the control deviation duration when the electrical signal is present. Such an arrangement can be implemented very easily and cost-effectively, and is easily adaptable to different applications.
In another advantageous embodiment of the invention, in step d) the pulse duty cycle of a PWM control device is controlled by the charge quantity of the memory arrangement, wherein the output signal of the PWM control device affects directly or indirectly the physical quantity to be controlled. Alternatively, the amount of charge in the memory arrangement can also directly control a signal, for example a DC signal (for example via an impedance transformer).
Execution of the method is fast if, in a modified embodiment of the invention, the control deviation is converted into the at least one electrical signal at the same time the control deviation is measured.
Alternatively, the control deviation is converted into the at least one electrical signal after the control deviation has been measured. The control deviation can then, before being converted into the electrical signal, advantageously be multiplied by a predetermined factor and the control deviation can be determined more frequently.
Additional details and advantageous embodiments of the invent
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Dieterle Roland
Karwath Arno
Rappenecker Herman
Martin David
Papst-Motoren GmbH & Co. KG
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