Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1991-09-18
1993-03-02
Ip, Paul
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318661, 318603, 901 26, 395 93, G05B 106
Patent
active
051912716
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention pertains to a process and a device for adjusting an axis, especially an axis of rotation, where many cycles of a drive means, such as a motor, are used to perform one cycle of the axis.
When using position-measuring systems with cyclic absolute or incremental position transducers, a problem arises in connection with the adjustment of the axis during the operation. Such a readjustment becomes necessary when parts of the control unit are replaced or when the position values carried in the control unit are lost due to disturbance.
It has been known from West German Offenlegungsschrift No. DE-OS 38,32,457 that the mechanical zero point marking on the axis can be scanned to adjust an axis of a cyclic absolute position-measuring system. However, it is sometimes difficult to perform this scanning during normal machine operation. On the one hand, ambient effects, such as external vibration induction, may cause disturbances. On the other hand, attached parts may prevent free access to the measuring site and the mechanical zero point marking.
SUMMARY AND OBJECTS OF THE INVENTION
Therefore, it is the task of the present invention to show a process and a device for adjusting an axis, which permits adjustment with simple and reliable means and also makes possible readjustment during the operation of the machine.
According to the present invention, an adjusting sensor, which represents a substitute for the mechanical zero point marking for the readjustment of the axis during operation is provided at the axis. The adjusting sensor is arranged in an exactly defined, predetermined position of the axis. If the cycle of the position-measuring system is lost, the axis can be readjusted by passing over the adjusting sensor. In this case, the adjusting sensor sends a signal to the axis control unit, which assigns the cycle value known from the adjusting sensor to the position-measuring system at this point. A position-measuring system with a cyclic absolute position transducer is thus completely adjusted. In contrast, a system with an incremental position transducer still requires referencing. The mathematical null of the axis control unit and consequently also the axis can be readjusted with the readjustment of the position-measuring system.
The adjusting sensor is arranged in the working range of the axis such that in the interest of unambiguous signal assignment, it is passed over, if possible, only once. Therefore, it is preferably seated on the limit switch drive mechanism of the axis. It may also be directly or indirectly connected to the axis in another manner, and depending on the size of the working range of the axis. If unambiguous signal assignment has been ensured in another way, the adjusting sensor may also be passed over several times in the working range of the axis.
Thus, the present invention permits simple and rapid readjustment of the axis and the position-measuring system during operation free from ambient effects. In addition, continuous checking of the position-measuring system can also be carried out with it.
The process according to the present invention and the corresponding device are suitable for any type of axes. The preferred field of applications is axes of rotation. Particular advantages are obtained in the case of use for axes of manipulators and multiaxial industrial robots.
The present invention also contains a particularly rapid, reliable, and convenient process for adjusting such an adjusting sensor. This process is performed once prior to shipment and under optimal conditions at the machine manufacturer. It is also performed after replacement of mechanical parts of the machine.
The adjustment process requires a position-measuring system with internal cyclic absolute signaling. This is defined, within the framework of the present invention, that the position transducer of the position-measuring system will deliver, within its cycle, absolute position values which can be read or obtained by incremental counting, depending on the transducer. Via
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Ip Paul
Kuka Schweissanlagen & Roboter GmbH
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