Electricity: motive power systems – Positional servo systems – 'sampling' systems including miscellaneous 'sampled data'...
Patent
1984-05-14
1985-11-19
Dobeck, B.
Electricity: motive power systems
Positional servo systems
'sampling' systems including miscellaneous 'sampled data'...
318561, 318571, 318616, 364178, G05B 2102
Patent
active
045544972
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to an acceleration/deceleration circuit and, more particularly, to an acceleration/deceleration circuit well-suited for driving, e.g., a moveable element of a machine tool or a hand of a robot.
In a control unit for controlling travel along the axes of a machine tool, a robot or the like, acceleration and deceleration generally are carried out so that the mechanical system will not be subjected to shock or vibration when starting and slowing down axial travel. Two of such acceleration/deceleration methods, described hereinbelow, are available. Though the case to be described relates to linear interpolation along two, i.e., X and Y axes, operation is entirely the same for cases where there are more than two axes and for circular interpolation, etc. Further, we shall let T represent a sampling period, F a commanded feed velocity, X a traveling distance along the X axis, Y a traveling distance along the Y axis, and S (=.sqroot.X.sup.2 +Y.sup.2) a traveling distance along a tangential direction.
The first acceleration/deceleration method comprises performing coarse interpolation in a coarse interpolator by obtaining a minute traveling distance component .sub..DELTA. S using the operation .sub..DELTA. S=F.T performed every sampling period T, and by obtaining traveling distance components .sub..DELTA. X, .sub..DELTA. Y along the X and Y axes using .sub..DELTA. S and the following equations: ##EQU1## These calulations are followed by performing acceleration and deceleration, with independent delays along the axes with respect to .sub..DELTA. X and .sub..DELTA. Y. FIG. 1 is a block diagram of a control apparatus to which the first acceleration/deceleration method is applied. A coarse interpolator 101 uses the feed velocity F and the traveling distances X, Y along the X and Y axes to compute coarse interpolation data .sub..DELTA. X, .sub..DELTA. Y from Eqs. (1) and (2), and applies the data .sub..DELTA. X, .sub..DELTA. Y to pulse distributors 102X, 102Y, respectively. The pulse distributors 102X, 102Y, which serve as fine interpolators, perform a pulse distributing operation based on the coarse interpolation data .sub..DELTA. X, .sub..DELTA. Y to generate distributed pulses XP, YP the number of pulses generated corresponds .sub..DELTA. X, .sub..DELTA. Y during one sampling interval.
The distributed pulses XP, YP are applied to respective acceleration/deceleration circuits 103X, 103Y, disclosed in the specification of U.S. Pat. No. 3,838,325. Each of the acceleration/deceleration circuits 103X, 103Y has the construction shown in FIG. 3. This assumes that each performs acceleration and deceleration in exponential fashion, as depicted in FIG. 2, during rise time and decay time, respectively. In FIG. 3, numeral 3a denotes a synthesizing circuit for combining the distributed pulses XP (YP) produced by the pulse distributor 102X (102Y), and output pulses XCP (YCP) from the acceleration/deceleration circuit 103X (103Y). Numeral 3b denotes a register for storing the pulses produced by the synthesizing circuit 3a. Numeral 3c designates an accumulator, and 3d denotes an adder for adding the contents E of the register 3b and the contents of the accumulator 3c each time a pulse P is produced at a certain pulse rate Fc. The result of the adding operation is stored in the accumulator 3c. With F as the pulse rate of the distributed pulses XP, and with Fo as the pulse rate of the output pulses XCP, we having the following equations: ##EQU2## where n represents the number of bits of the accumulator 3c. Equation change (3) represents the increment of the register 3b per time unit, and Eq. (4) expresses the number of carry pulses (output pulses XCP) produced by the accumulator 3c per time unit. Obtaining the output pulse rate Fo from Eqs. (3) and (4) gives us the following: exponentially at start-up and decelerated exponentially when the movable object is brought to rest.
Returning to FIG. 1, the output pulses XCP, YCP accelerated and decelerated exponentially by the acceleration/de
REFERENCES:
patent: 3838325 (1974-09-01), Kobayashi
patent: 4357664 (1982-11-01), Imazeki et al.
patent: 4368433 (1983-01-01), Imazeki
patent: 4486693 (1984-12-01), Hamati et al.
patent: 4488098 (1984-12-01), Shimonou
Kawamura Hideaki
Nozawa Ryoichiro
Sasaki Takao
Dobeck B.
Fanuc Ltd.
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