Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1996-07-01
1998-12-08
LaBalle, Clayton E.
Electrical generator or motor structure
Dynamoelectric
Rotary
318696, H02K 3704, H02P 812, H02P 822, H02P 832
Patent
active
058474757
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
For operating instruments with pointers, especially in vehicles, until now along with mechanical tachometers, bimetallic instruments and rotary coil instruments, rotary magnet quotient measuring mechanisms (DQMs) have predominantly been used. Recently, however, (two-phase) stepper motors are gaining more and more currency--especially in Europe. Such stepper motors are used both in the form of direct drives (NMB) and--preferably--in the form of gear motors (made by switec and VDO).
For direct drives, for reasons of torque and cost, only claw pole (tin-can) stepper motors have been used until now. At stepping angles of typically 7.5.degree. to 15.degree. for the requisite resolution of approximately 0.1.degree., these motors require triggering in the microstep mode. However, the standard types made in large-scale mass production exhibit a highly nonlinear relationship between the electrical phase angle and the mechanical output angle, so that the conventional sinusoidal triggering produces an entirely unacceptable jerky motion of the pointer. The reason for this is--among others--the mechanical resting moment of the motors.
Specially optimized types now exist that even with sinusoidal triggering have acceptable synchronous properties. However, these motors are more expensive to construct yet have poorer mechanical performance data than the corresponding standard types. Even then, their performance over the temperature and voltage range is not entirely satisfactory. Moreover, for the zero position or position control they require additional sensors, such as a Hall IC.
SUMMARY OF THE INVENTION
The method according to the invention for triggering a stepper motor having the characteristics of the body of the main claim has the advantage over the prior art that because of the correction of the trigger pulses, an especially simple encoder (digital angle encoder) from the "lowest-cost" price range can be used, and thus costs not much more than a zero sensors that detects the zero position of the stepper motor. Thus along with the zero position, the motion control of the stepper motor can be detected as well, and above all can also be used for correcting the microstep performance, and the resolution required is far below that needed in conventional control processes. As a result, it is possible to trigger the stepper motor successfully with a resolution of 0.1.degree., for instance, even though the angle encoder used cannot remeasure this high resolution.
By means of the provisions recited in the dependent claims, advantageous further features of and improvements to the method disclosed in the main claim are possible.
BRIEF DESCRIPTION OF THE DRAWINGS
An exemplary embodiment of the invention is shown in the drawing an described in further detail in the ensuing description.
FIG. 1 shows a first block circuit diagram in accordance with the prior art.
FIG. 2 shows a first graph;
FIG. 3 shows a second graph;
FIG. 4 shows a second block circuit diagram;
FIG. 5 shows a third block circuit diagram;
FIGS. 6a and b each show a second graph;
FIG. 7 shows a fourth block circuit diagram;
FIG. 8 shows a fifth block circuit diagram;
FIG. 9 shows a third graph;
FIG. 10 shows a fourth graph; and
FIG. 11 shows a fifth graph.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The first block circuit diagram of FIG. 1 shows a known stepper motor 3, on whose shaft an encoder or angle encoder 4 is nondetachably disposed. The angle encoder 4 has a stationary photoelectric barrier 6, past which the marking of a code disk 7, which is nondetachably connected to the shaft of the armature of the stepped motor 3, passes. Also secured on the shaft by way of example is a pointer 8 for a gauge, with which a stationary scale disk 5 is associated. The gauge may be mounted in the instrument panel of a motor vehicle. The stepper motor 3 is supplied by an end stage 2 with current pulses that are generated by a preceding controller 1. The known controller, at a point 10, compares a command value 11 with the value measured by
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Ehrmann Martin
Herzog Bernhard
Hovestadt Uwe
Rauch Hans
LaBalle Clayton E.
Robert & Bosch GmbH
Striker Michael J.
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