Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1998-03-10
2000-09-26
Allen, Stephone B.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
318640, G01D 5245
Patent
active
061245887
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The instant invention relates to a method for position determination, particularly that of a rotating drive element. The invention further relates to a measuring system, which comprises an absolute and an incremental measuring subsystem.
BACKGROUND OF THE INVENTION
It is necessary for the precise control of an electrical drive to always detect the position of the revolving rotor with absolute accuracy and to know the absolute rotor position already at the start of a rotary movement, in particular in connection with synchronous motors. Various rotatory measuring systems are known for this, which transmit the detected measured position values over respectively several connecting lines to a subordinated evaluation unit, or respectively an electronic follow-up device. In turn, the evaluation unit takes over the drive control as well as further control function, if required. The least possible outlay in respect to the measuring systems used in this is desired.
However, relatively elaborate systems are the result of the employment of highly accurate absolute measuring systems, which possibly also provide incremental data, or of incremental measuring systems also providing absolute commutation signals and whose data are transferred to the evaluation unit. The parallel transmission of absolute and incremental position data, as well as of the reference marker signals, if required, requires a large number of connecting lines.
To reduce the number of required connecting lines between the respective measuring systems and the subordinated evaluation unit, the transmission of the measured values and other data by means of a multiplex operation over as few as possible signal connections is known, for example.
OBJECT AND SUMMARY OF THE INVENTION
It is the object of the instant invention to create a method for position determination, in particular for detecting revolving movement of a rotating drive element, as well as a measuring system suitable for this, which result in the smallest possible outlay. In this connection a reduced outlay in regard to the required signal transmission lines between the measuring system and the subordinated evaluation unit is particularly desired. Furthermore, a sufficiently precise and dependable position determination should be assured as soon as possible following the start of the rotating drive element.
The measuring system in accordance with the invention, or respectively the method in accordance with the invention, now provide the opportunity for detecting the absolute position of a rotating drive element at any point in time during the rotary movement. At the start of the rotary movement a control of the drive, i.e. particularly the required drive commutation, is already possible with sufficient precision on the basis of the position data transmitted to the evaluation unit. In this case the position data transmitted in digital form are based on the position data of the absolute measuring subsystem used, i.e. the resolution of the position data for the drive commutation transmitted at this point in time depends on the available resolution of the absolute measuring subsystem. As soon as a reference marker, whose absolute position is known, has been passed for the first time, a highly accurate absolute measured position value for the subsequent operation of the drive, or respectively its control, is available, together with the measured values of the incremental measuring subsystem, and is transmitted to the evaluation unit. In this connection there exist various options for producing the absolute relationship, i.e. in particular in view of the employment of one or several reference markers.
Further than that, the result is the desired reduction of the required connecting lines between the actual measuring system and the subordinated evaluation unit, since no parallel transmission of the position data of the absolute and the incremental measuring subsystems as well as the reference marker signals to the evaluation unit is necessary. The generation of absolute
REFERENCES:
patent: 5686804 (1997-11-01), Siraky
Bielski Steffen
Hagl Rainer
Huber Helmut
Allen Stephone B.
Johannes Heidenhain GmbH
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