Coded data generation or conversion – Digital pattern reading type converter – With directional discrimination
Patent
1993-11-10
1995-10-24
Young, Brian K.
Coded data generation or conversion
Digital pattern reading type converter
With directional discrimination
H03M 148
Patent
active
054613752
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to forward/backward counting devices.
Forward/backward counters are generally used in robotics and sometimes in metrology. They are involved in systems enabling the position of various moving bodies to be referenced. Thus they are present, for example, in the servocontrol loops intended for controlling the positioning of motor shafts.
In order to correct the position of an object, the indication giving the actual position of the said object is compared with an external set-point. The object to be controlled is linked to a position coder which delivers two signals in quadrature. These signals are sent to a forward/backward counter whose function is to provide an indication of position in binary code. This indication is the absolute address of the object. This absolute address cannot be sampled at any time: it is only defined within certain time windows and outside of these windows it may be erroneous.
It is known to those skilled in the art that the forward/backward counter must then be equipped with an output register controlled in synchronism with the signals leaving the position coder.
The invention does not have these disadvantages.
One of the subjects of the invention is a forward/backward counting device intended for providing an absolute address in binary code, the said address enabling the position of an object to be deduced from signals leaving a non-absolute position coder linked to the said object, characterized in that it comprises means intended for generating a partial address consisting of the lowest order bits of the said address expressed in reflected binary code or any other equivalent code.
Other characteristics and advantages of the invention will emerge on studying a preferred embodiment, given with reference to the attached figures in which:
FIG. 1 represents the block diagram of a position servocontrol using a forward/backward counter according to the prior art,
FIG. 2A represents the block diagram of a forward/backward counter according to a preferred embodiment of the invention,
FIG. 2B represents an assembly of logic circuits coming into the construction of the forward/backward counter according to the invention,
FIG. 3 represents the timing diagram for the forward/backward counter described in FIG. 2,
FIG. 4 represents the curve for determining, by linear extrapolation, the absolute addresses in the case where the forward/backward counter provides merely a partial address,
FIG. 5 represents, symbolically, an algorithm for determining the absolute address in the case where the forward/backward counter provides merely a partial address,
FIG. 6 represents the block diagram of the position servocontrol using a forward/backward counter device according to a preferred embodiment of the invention,
FIG. 7A represents the chart of the internal states of a five-state cyclic forward/backward counter,
FIG. 7B represents the input signals, the corresponding internal state and the output signals of the five-state cyclic counter,
FIG. 8 represents the block diagram of the position servocontrol using a forward/backward counter according to a second embodiment of the invention .
In all the figures, the same references designate the same elements.
The servocontrols described by FIGS. 1, 6 and 8 are, in essence, produced with the aid of a microprocessor. Thus, each of the devices situated in area 100 of the said figures is the symbolic representation of one operation of the servocontrol algorithm.
FIG. 1 represents the block diagram of a position servocontrol using a forward/backward counter according to the prior art. The object to be controlled is, for example, a motor shaft.
A coder 1 captures the position of the motor shaft A of the motor M. In a general way, this coder is a non-absolute coder which delivers two signals S1 and S2 in quadrature.
In order to reconstruct an indication giving the absolute position of the motor shaft, the use of a forward/backward counter 2 is then required. The forward/backward counter 2 is composed of two devices: a first device 21 whi
REFERENCES:
patent: 4041483 (1977-08-01), Groff
patent: 4714913 (1987-12-01), Cohen
patent: 5091643 (1992-02-01), Okutani et al.
Art Tech Gigadisc
Young Brian K.
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