Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1987-03-05
1989-07-25
Ro, Bentsu
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318561, G05B 1304
Patent
active
048517500
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field Of The Invention
The present invention relates to improvement in tracer control equipment, and more particularly to tracer control equipment which enables deterioration control at a jerk point in the configuration of a model to be optimum to the configuration of thereof at that particular point.
2. Description of the Related Art
In the case of tracing a model M with a configuration as shown in FIG. 4, if the jerk points (a) to (c) in the configuration of the model are traced at the same speed as that for flat surfaces of the model, a cutter can bite into a workpiece at the jerk point (a) and a stylus ST can move out of contact with the surface of the model M at the jerk points (b) and (c). To avoid this, it is a general practice in the prior art to compare the variation of a displacement signal from a tracer head per unit time with a preset value and reduce the feed rate to a predetermined value while the former is greater than the latter. That is, since the displacement signal from the tracer head undergoes an abrupt change at each jerk point in the configuration of the model and the variation of the displacement signal per unit time also varies abruptly at the jerk point, it is possible to prevent the biting of the cutter into the workpiece and other similar trouble by controlling the feed rate as mentioned above.
According to the above-mentioned prior art example, however, when the changing ratio of the displacement signal exceeds a predetermined value, the feed rate is reduced to a predetermined value regardless of the configuration of the model at the jerk point so that it is impossible to perform optimum deceleration control corresponding to the configuration of the model at the jerk point. Namely, according to the prior art example, the feed rate during deceleration must be set low so that the cutter will not bite into the workpiece even when the stylus traces a sharp corner of the model. Consequently, when deceleration control takes place at a gentle corner portion, the feed rate undergoes an abrupt change, which results in the problem of deterioration of the workpiece surface.
SUMMARY OF THE INVENTION
The present invention has as an object enabling optimum deceleration control corresponding to the configuration of the model at a jerk point therein.
To solve the above-noted problem, the tracer control equipment of the present invention, which controls the relative feed rate between the model and the tracer head tracing the surface thereof, in accordance with the displacement signal from the latter, is provided with detecting means for detecting the variation of the displacement signal per unit time, decision means for comparing the detected variation of the displacement signal with a plurality of threshold values of different levels and deciding which of regions defined by the threshold values the variation of the displacement signal belongs to, and deceleration control means whereby the relative feed rate between the tracer head and the model is reduced to and held at a value corresponding to the result of the decision by the decision means during a period from the time when the variation of the displacement signal is decided by the decision means to have exceeded the threshold value of the lowest level of the other threshold values to the time when it is decided to have returned to a value smaller than the threshold value of the lowest level.
According to the tracer control equipment of the present invention, since the feed rate for deceleration control is determined depending upon which of the regions defined by the plurality of threshold values the variation of the displacement signal per unit time belongs to, optimum deceleration control can be achieved corresponding to the configuration of the model at the jerk point. Furthermore, since the deceleration control means continues its deceleration control until the variation of the displacement signal becomes smaller than the threshold value of the lowest level again after having exceeded it, deceleration
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patent: 3991354 (1976-11-01), Rosa et al.
patent: 4328450 (1982-05-01), Gabor
patent: 4357664 (1982-11-01), Imazeki et al.
patent: 4394608 (1983-07-01), Tryber et al.
patent: 4603285 (1986-07-01), Matsuura
patent: 4638230 (1987-01-01), Lee
patent: 4646225 (1987-02-01), Matsuura
Fanuc Ltd.
Ro Bentsu
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