Coded data generation or conversion – Digital pattern reading type converter – Incremental
Reexamination Certificate
2003-04-28
2004-11-02
JeanPierre, Peguy (Department: 2819)
Coded data generation or conversion
Digital pattern reading type converter
Incremental
C341S009000
Reexamination Certificate
active
06812861
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
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STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT
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REFERENCE TO AN APPENDIX
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for automatic generation of several electrical pulses using numeric default values, which process is particularly suitable for simulating an incremental encoder for sequential digital counting of pulses, where the counter result corresponds to linear or angular displacement values. A value generator is used which generates and outputs the default values repeatedly within allocated first cycle times. The default values are then used by cyclic detection, calculation and control means and a pulse switching interface controlled thereby which has one or more outputs for the pulses or pulse sequences. The invention further relates to a digital electronic data processing apparatus suitable for performance of the said process.
2. Description of the Related Art
Processes for generating parallel electrical pulse sequences are used in incremental methods of length and angle measurement (see e.g. Alfons Ernst “Digital Length and Angle Measurement Technology” Verlag Moderne Industrie, Landsberg/Lech, page 8 ff). Sinusoidal sampling signals offset by 90° to each other are converted by means of comparators into rectangular pulses giving two pulse sequences phase offset by 90° to each other. These are supplied to a counter in which counting pulses are first derived from the signal flanks. At the same time the signals are passed to a direction discriminator which determines the counting direction and passes the counting pulses to the plus or minus input of an up and down counter. The counting result corresponds to the displacement path and can be shown in a display or supplied to a computer or controller. Such processes for determining the displacement path by counting pulses or measurement steps are known as incremental measurement processes.
Resolvers are also known which in conjunction with a suitable analysis circuit can implement an absolute measurement system within one revolution. By means of interpolation, measurement steps can be generated which are less than one-quarter of the period of the sampled signals. Known interpolators provide not only the interface for the absolute measurement system but optionally also an incremental interface to allow use in conjunction with conventional controls.
In particular in connection with the use of resolvers as position encoders it is known to simulate and output incremental encoder signals for subsequent control electronics (see DE journal “Electronics”, Vol. 8/1994, page 48, page 60). Here the incremental encoder simulation is normally achieved using a position control circuit which outputs as a variable a set frequency for a frequency generator. Reference is made to the description below of
FIG. 1
for further details. One disadvantage of this known solution is that this is a control circuit which can only work if a control deviation is present. Thus in the least favorable case, depending on the selected dynamics of the controller, even when stopped i.e. if an unchanging position is to be shown, a very high output frequency (up to more than 1 MHz by toggling of a track) can be present, which is difficult for following electronics to interpret. This time behavior of the control circuit can lead to an undesirable inherent dynamic of the entire adjustment and control system dependent on the incremental encoder simulation. A further disadvantage lies in the use of the frequency generator, the output pulses of which reflect only a nominal or set frequency but do not have a direct relation to the position default values for simulating the incremental encoder. Furthermore the necessary hardware expense cannot be ignored: as well as a position controller, a frequency generator and a counter module, summing points are also required (see
FIG. 1
below). To remedy this, implementation of the control circuit in an existing signal processor is possible but this only allows limited sampling times in conjunction with a restricted frequency range, reduced resolution and non-optimum precision.
BRIEF SUMMARY OF THE INVENTION
The invention is based on the object of specifying a process for incremental encoder simulation with increased resolution and precision, increased stability and operating reliability and a reduced complexity of the necessary hardware. The simulation should also be able to work with improved dynamics, where an improved linearity can be achieved in the correlation between the position change and the output pulse frequency. In addition the process primarily intended for incremental encoder simulation can be used outside this area of application as a general pulse-generating process for a multiplicity of further possible uses.
The object is achieved in a process with the features cited initially, in that the program and/or circuitry of the calculation and control means are designed:
to detect the current default value and determine the difference value from the current and a previous default value or an incremental value per first cycle time, which incremental value was counted up or down previously in accordance with previous default values or difference values,
to convert the difference value into control signals for the binary interface, a process which is repeated within several second cycle times, the total duration of which does not exceed the first cycle time of the value generator,
and to dimension the number or frequency of the pulses or pulse flanks triggered per first cycle time according to the difference value concerned, preferably directly proportional to the difference value.
The new solution approach is therefore characterized in that no control circuit is used as in the prior art; rather the pulses for example of tracks A and B in incremental encoder simulation are output controllably in direct proportional to the incoming position default value. This direct correlation of the pulse output to the incoming default, in particular position values, gives the advantage that when the default value remains unchanged, no further pulses or pulse flanks are output. Toggling of a track with very high frequency due to unavoidable inherent dynamics of control circuits is prevented with the solution according to the invention. The number or frequency of the output pulses or pulse flanks is dimensioned directly according to the difference value of two default values of different preferably successive cycle times of the value generator. If the default remains unchanged (which can e.g. correspond to a stopped position), the difference has the value of zero so the pulse switching interface is not switched to generate pulses.
According to an advantageous embodiment of the invention the default value is simulated internally in the calculation and control means via integration of the difference value from the previous default value or incremental value, where the integration calculation process is spread divided over the second cycle times occurring within a first cycle time. Depending on the result of the integration calculation process, in each of these second cycle times it is checked whether the pulse switching interface should be triggered to output corresponding pulses or pulse flanks.
According to a particularly advantageous process variant, within the calculation and control means a variable incremental value is kept or managed which tracks the current default value within each cycle time according to the difference value. During the tracking process, depending on the incrementing or decrementing, pulse or pulse flanks are generated via the pulse switching interface.
To produce an absolute correlation, in particular an absolute position, in incremental (measurement) counting processes it is normal to generate a so-called reference pulse. For this according to one embodiment of the invention it is provided that the calculation and control means contain one or more reference
Baumuller Anlagen-Systemtechnik GmbH & Co.
Foster Frank H.
Jean-Pierre Peguy
Kremblas, Foster Phillips & Pollick
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