RU2525845C1 - Device for realisation of cyclic movements - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: device comprises a setting unit, three summators, a sensor of output coordinate of a regulation object, delay units, a filter and additional delay units, connected to each other, as specified in the invention. All delay units are made with parameters determined in accordance with time coordinates of points of transition characteristic of the regulation object, and the delay time of the first delay unit also depends on the cycle time.

EFFECT: increased accuracy of realisation of cyclic movements.

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Description

The proposed device relates to electromechanics and automation and can be used to implement cyclic movements. This can be manipulators, lathes for processing non-circular parts and other devices that are characterized by cyclic movements.

A device is known in the form of a continuous servo system for automatic control of cyclic action, in which under certain conditions the control error decreases from cycle to cycle (USSR Authors Certificate No. 723510, Bull. Invention No. 11, p. 193, 1980). Reducing errors in the device is achieved by including in the feedback circuit of a system of memory devices that fix systematic errors of the current cycle, and then, according to a certain algorithm, error reduction is implemented for the next cycle.

The known device has disadvantages.

The device implements a version of the tracking system with a hyper-stable control object, which suggests, according to the theory of automatic control, the positivity of the real part of its complex transfer coefficient. However, in practice this case is quite rare, therefore, the aforementioned device has limited use, only for objects of regulation of a low order. The use of the device in a system with an object of regulation of the second order and higher leads to instability of the system, which is a disadvantage.

A device in the form of a two-channel electric drive is also known, RF patent No. 2223592, 02/10/2004, bull. No. 4 (prototype), containing an actuator located on a mobile platform, a first electric drive for moving the mobile platform, a sensor for moving the mobile platform, a first block for setting the movement of the mobile platform, connected in series with the first adder, the second input of which is connected to the sensor for moving the mobile platform, and the output is connected to the input of the first electric drive moving the movable platform, the second electric drive moving the actuator relative to the platform, the sensor the executive body relative to the platform, the second unit for setting the movement of the executive body, connected in series with the second adder, the second input of which is connected to the displacement sensor of the moving platform, the third input of which is connected to the displacement sensor of the executive body relative to the platform, the third adder, filter. In addition, it is equipped with a block of a dynamic model of the second electric actuator moving relative to the platform, a fourth adder, a first and second delay blocks, a proportional block, and a block of a dynamic model of the second electric drive connected to the output of the first adder, the output connected to the first input of the fourth adder, the second the input of the fourth adder is connected to the output of the first block of the job of moving the moving platform, the third input of the fourth adder is connected to the output of the second about the unit for setting the movement of the executive body, the fourth input of the fourth adder is connected to the displacement sensor of the executive body relative to the platform, and the output of the fourth adder is connected to the input of the proportional block connected in series through the third adder to the first delay unit, the output filter is connected to the second input of the third adder; the input of the filter is connected to the output of the second delay unit, the input of the second delay unit is connected to the output of the first delay unit and simultaneously with the fourth input of the second adder.

The said device is intended for the implementation of cyclic movements in a two-channel transverse feed electric drive in machines for turning non-circular parts. To reduce cyclic errors, it implements the principle of self-training as applied to the exact channel. The device uses sequential correction of the control object, the correcting device is implemented as an advance link, and the lead time is determined from the approximation of the transition function of the regulation object with one equivalent delay link. At the same time, the self-learning circuit includes two series-connected delay units for the total cycle time T, covered by feedback through the filter.

A correction signal in the device is generated at the output of the first delay unit and through the fourth input of the second adder is fed to the control object - the electric drive of the exact channel. The device operates stably in the entire frequency range and with high-order control objects, which is ensured by the corresponding parameters of the second delay block, as well as the filter parameters in feedback, covering both delay blocks. Moreover, the presence of a filter leads to the appearance of a steady-state cyclic error, the magnitude of which is directly related to the filter parameters (see Nikolsky A.A. Stability of self-learning electric drives for supplying metal cutting machines and the accuracy of self-learning processes // Electricity, 2007, No. 5. - P.38- 45).

The technical problem solved by the invention is to reduce the steady-state error in the implementation of cyclic movements. This problem is solved by improving the correction of the regulatory object, which allows, while maintaining stability, to change the filter parameters in such a way as to reduce the steady-state cyclic error. In this case, the correction should be practicable.

The technical effect achieved by the invention is caused by the use of correction based on a more accurate consideration of the parameters of the dynamic characteristics of the control object by approximating its transition function using n delay units (n> 1, the greater n, the higher the effect).

The problem can be solved if, in series with the control object, include such a correcting device, the complex transfer coefficient of which will be complex conjugate with the transmission coefficient of the control object.

The problem is solved in that the known device for the implementation of cyclic movements, containing a task unit, the output of which is connected to the first inputs of the first and second adders, the second inputs of the first and second adders are connected to the sensor output of the output coordinate of the control object, the input of which is connected to the output of the second adder , the output of the first adder through the first input of the third adder is connected to the input of the first delay unit, the output of which is through the second delay unit and the fil mp connected to the second input of the third adder and simultaneously to the third input of the second adder according to the invention is provided connected to the output of the first delay block additional delay units whose outputs are connected to respective inputs of the second additional adder. Moreover, all delay blocks are made with parameters determined in accordance with the time coordinates of the points of the transition characteristics of the control object, and the delay time of the first delay block also depends on the cycle time. We consider this case in more detail.

If the transition function of the control object h (t) as its reaction to a single jump in the input control signal (see, for example, Feldbaum A.A., Butkovsky A.G. Methods of automatic control theory. - M .: Nauka, 1971) is known, then it can be represented as a set of n time-discrete values of h (t), where i = 1, ..., n. If the number n is sufficiently large (in the limit n → ∞), then the transfer function of the regulatory object under these conditions, taking into account the Laplace transform, can be written in the form:

; (n→∞), $$W_o\left(p\right)={\displaystyle {\sum }_{i=\mathrm{one}}{\sigma }_i{e}^{-p{t}_i}}$$

; (n → ∞),

where σ _i = h (t _i ) -h (t _i-1 ) are the stepwise increments of the discrete values of the transition function for the corresponding discrete time moment t _i . According to the theory of automatic regulation, such a transfer function of the control object corresponds to a complex transfer coefficient:

. $$W_o\left(j\omega \right)={\displaystyle \sum _{i=\mathrm{one}}^n{\sigma }_i{e}^{-j\omega t_i}}$$

.

Based on the above task, this transfer coefficient corresponds to the complex conjugate transmission coefficient of the correcting device in the form of:

$$W_k\left(j\omega \right)={\displaystyle \sum _{i=\mathrm{one}}^n{\sigma }_i{e}^{-j\omega t_i}}$$

whose transfer function, taking into account the above:

; (n→∞). $$W_k\left(p\right)={\displaystyle \sum _{i=\mathrm{one}}^n{\sigma }_i{e}^{p{t}_i}}$$

; (n → ∞).

со своими весовыми коэффициентами σ_i. Однако звенья опережения в обычных следящих системах не реализуемы.The resulting transfer function of the correcting device is structurally represented in the form of n parallel connected advance units $$e^{p{t}_i}$$

with their weights σ _i . However, lead units in conventional tracking systems are not feasible.

Cyclic systems, in contrast to conventional ones, always include delay links for the time of cycle T. Moreover, if we assume that the value of n is large enough, but of course the magnitude, the above correction device, with advance links, as will be shown below, is realizable.

In practice, the number n can be set, for example, on the basis of experimentally obtained (using modern computer tools) time-discrete values of the transient response of the control object h (t _i ). In this case, the necessary lead time t _n determined by the transition function of the control object should be less than the cyclic period T. This condition allows you to implement a correction device with the previously obtained transfer function. In addition, when such a corrective device is turned on between the output of the delay link for the period of cyclicity T and the input of the control object, as a result of structural transformations according to the well-known rules of the theory of automatic control, the lead units are converted into delay links implemented in practice, as was done in the prototype for a single link advances.

The drawing shows a block diagram of the proposed device.

The delay time of the first delay block 6, according to the block diagram, is less than the cyclic period T by time t _n , the delay time of the second delay block 7 is t _n , and the delay times of the remaining, additional n-1 blocks are determined by the formula: t _n -t _i , where i = 1, n-1. In addition, the values of the coefficients σ _i with their weights are taken into account directly when summing on the second adder 3.

The proposed device for implementing cyclic movements contains a task unit 1, the output of which is connected to the first inputs of the first 2 and second 3 adders, the second inputs of the first 2 and second 3 adders are connected to the output of the sensor 4, the output coordinate of the control object 5, the input of which is connected to the output of the second adder 3, the output of the first adder 2 through the first input of the third adder 4 is connected to the input of the first delay unit 6, the output of which is connected through a second delay unit 7 and the filter 8 is connected to the second the input of the third adder 4 and simultaneously to the third input of the second adder 3. In addition, according to the invention, it is equipped with additional delay units connected to the output of the first delay unit 6 n-1, the outputs of which are connected to the corresponding additional inputs of the second adder 3, all delay units made with parameters determined in accordance with the time coordinates of the discrete points of the transition function of the regulation object 5, and the delay time of the first delay unit 6 also depends on the time cycle .

The device operates as follows.

The cyclic reference signal is supplied from the output of reference block 1 simultaneously to the first inputs of the first 2 and second 3 adders. The error signal in the current cycle in the form of the difference between the reference signal and the sensor output signal of the output coordinate 4 is supplied, respectively, through the first and second inputs of the second adder 3 to the input of the control object 5. The same error signal is generated at the output of the first adder 2 and, after summing with the output signal of the filter 8, is fed to the input of the first delay unit 6. The output signal of the first delay unit 6 is behind the input by the previously specified value T-t _n . The control signal on the current cycle is generated in the second adder 3 after summing the output signals of the first delay unit 6 and n-1 additional delay units, in accordance with their weights. At the same time, in accordance with the principle of self-learning, the control signal acts on the control object 5 in such a way that, compared with the previous cycle, the errors are reduced, and the steady-state cyclic error reaches its minimum value.

Modeling of cyclic processes in the proposed device shows that the sequential correction described above ensures the stability of the system in the entire frequency range and with high-order control objects. At the same time, in comparison with the prototype, the requirements for the necessary filtration are significantly reduced, which allows you to change the filter parameters and thereby significantly reduce the steady-state cyclic error, improve the accuracy of the job. The observed effect of the application of the proposed device is caused by a correction based on a more accurate account of the parameters of the dynamic characteristics of the control object by approximating its transition function using n delay units (n> 1, the greater n, the higher the effect).

Claims (1)

A device for implementing cyclic movements, comprising a task unit, the output of which is connected to the first inputs of the first and second adders, the second inputs of the first and second adders are connected to the sensor output of the output coordinate of the control object, the input of which is connected to the output of the second adder, the output of the first adder through the first input the third adder is connected to the input of the first delay unit, the output of which is connected through the second delay unit and the filter in series to the second input of the third adder and simultaneously to the third input of the second adder, characterized in that additional delay units are connected to the output of the first delay unit, the outputs of which are connected to the corresponding additional inputs of the second adder.

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