SU808886A1 - Device for measuring load torque of a dc motor - Google Patents

Description

and therefore call for additional error.

The purpose of the invention is to improve accuracy.

This goal is achieved by the fact that the known device is equipped with a dividing unit and a series-integrated integration unit and a proportional-integrating dynamic unit covered by feedback ;; The output of the flux measurement unit is connected to the multiplication unit, the output of which is connected to the input of the integrator, the outputs of the EMF sensor and the flux measurement unit are connected to the inputs of the split unit, and its output is connected to the input of the proportional integrator unit. The EMF sensor is equipped with a variable resistor with a sliding contact with two extreme and one intermediate pins, a decisive amplifier and three capacitors, two of which are connected in parallel with the tachometer bridge resistors, and the third between the sliding contact and the intermediate output of the variable resistor, the extreme terminals of which are connected respectively with the output of the tachometer bridge and with the output of the cutting amplifier,; and the intermediate terminal of the variable resistor is connected to the input of the decider of an amplifier, the output of which is connected to the input of the dividing unit. The drawing shows the functional electrical circuit of the proposed device.

The electric drive contains a motor with windings of core 1 and independent excitation 2, root 1 winding and excitation winding 2 are connected to sources 3 and 4 of controlled voltages, respectively.

The device for determining the load moment comprises a current sensor 5, a magnetic flux sensor 6 and a sensor

7EDS electric motor drive unit

8 integration, proportional integration of block 9, multiplication and division blocks 10 11. Sensor outputs

5 current and magnetic flux 6 are connected to two inputs of multiplication unit 10, the outputs of which are connected to the input of integration unit 8. The output of the latter is connected to the input of the proportional-integrating unit 9 installed at the output of the device, the output of which is connected to the input of the integrating unit 8. The output of the sensor 7 EMF of the engine is connected to the input of the block 11 division, the input of the divider which is connected to the output of the sensor

6 magnetic flux, and the output of the block

11 divisions are connected to the input in proportion to the integrated unit of block 9.

Sensor 7 EMF of the motor drive is made in the form of a tachometer bridge, the shoulders of which include the windings of the core 1 and the additional poles 12 of the engine and two resistors 13 and 14. Sensor 7 also contains a decisive amplifier 15, an additional resistor 16 with a sliding contact 17 and an intermediate terminal 18 to three capacitors 19-21, the first 19 and second 20 capacitors being connected in parallel to the first 13 and second 14 resistors of the tachometer bridge, and the third

the capacitor 21 is connected between the sliding contact 17 and the intermediate terminal 18 of the additional resistor 16. The extreme terminals 22 and 23 of which are connected respectively to the output of the ta-: geometric bridge and to the output

decision amplifier 15, and the intermediate terminal 18 of an additional resistor 16 is connected to the input of decision amplifier 15.

The output voltage of the device

equally:

lJfeMX - HMn + ptnu P Turr, u

where KH is the scale factor relating the output voltage of the device with the load moment mc to

steady state To, Tnu constant time

block 8 integration and proportional-integrating unit 9;

n (1 - isodrome time of block 9 f

KV Ker is the scale factors of the sensors of current 5 and magnetic flux G i Kf, is the transfer coefficient of the multiplication unit 10.

To implement equation (1), the time of block 8 is integrated and is chosen from

Kf Ktj.Kn E

12)

I and in - - -----) KEKDSESn

de D

-Trinted torque and engine power;

-scale factor datK, chika 7 EMF;

K d - transfer coefficient

block 11 division; Cgt Sm - constructive constants

engine

As follows from equation (1), the device for determining the moment of load of the electric drive is the dynamic element of the second type. Enter the designation L. , / Ctiu

(with rUTho ifivi where ta) c.H is the natural frequency of the n damped oscillations and the relative damping coefficient. The change in the output voltage of the device, ix ° The function of the moment in the electric drive of Mi depends significantly on the magnitudes and relative position of the zero: H-4 2 & and two poles of the transfer function of the device, which with (1 are complex conjugate: 1 -, (- e.,), where J Y-1, and with 1, the poles are real and are defined by the dependencies: ri- (Jt ( -C,);. -7сЛм) The relative distance by the first pole and zero is characterized by the dependence: The transition process under the condition, 1 is almost monotonic and is determined only by the second (far from the PERMINENT axis) real pole, and the transition time tfi percent accuracy) is determined by the dependence:. t .. which corresponds to the values of l / u) 0.302 / i) with the change of s in elah (or change D in the range 0, 0.01). Given the required time value of the process t ,,, you can determine the required values, or A from the expressions: tn-K e;) as well as the directly required isodrome time

g

" P

ai

Os

which ensures that the quality of the transient process meets the requirements imposed on it. At the same time, the device provides a zero steady-state determination of the load moment as in the case of the introduction of a decisive amplifier 15, an additional resistor 16 with a sliding contact 17 and an intermediate terminal 18 and the third capacitor 21 ( Cj) ensures the inertia-free sensor 7 of the EMF of the motor of the electric drive;

When the sliding contact 17 is installed to the right of the intermittent change of this moment, and when it is linearly changed. Having established with the error on acceleration, the corresponding to the parabolic nature of the change in the load moment during the acceleration of the change in the moment, has the final value defined by the expression: ... q -. The choice of the EMF value of this error is-. It can be reduced to an acceptable level. Ensuring high accuracy also contributes to the implementation of the sensor 7 EMF of the motor drive. The static equilibrium of the tachometer bridge is ensured by the selection of the active resistors of its arms:. where R, Rj are the resistances, the first 13 and the second 14 resistors of the tachometer bridge} Rq, Cd are the resistances of the windings of the core 1 and the additional poles 12 of the electric drive motor} - “-A inductance of the windings 1 and 12. As is known, even when the condition of static equilibrium is fulfilled tachometer bridge due to the threaded inductances in the core circuit and. A thermometric bridge is not an inertia-free link, and in the absence of capacitors 19 and 20, the influence of a change in voltage U and source 3 on Bbtxcgi Hoe unavoidable is the voltage of the tachometer bridge, resulting in a dynamic error in determining the motor EMF and torque of the electric drive. The introduction of capacitors 19 and 20 eliminates the influence of the voltage and source of the controlled voltage on the output voltage of the tachometer bridge when selecting the values of these capacitors in accordance with the dependencies: s, - - output pin 18 with the division factor The right side of the resistor 16 is bs (between intermediate output terminal 18 and the output of decisive amplifier 15). At the same time, the output voltage of the soldering amplifier is characterized by: U (; ° Rf.

Claims (2)

When choosing the parameters С j, Of, R ,. , R i / i in accordance with dependencies: od -А. where Ry, the resistance (the meter output of the tachometer bridge and intermediate terminal 18) and the right (between intermediate terminal 18 and the output of the decisive amplifier 15) parts of the additional resistor 16, provide a non-inertial connection between the motor EMF and the sensor output of this EMF through a scale factor Kg, which eliminates the additional error in determining the EMF and the load moment of the electric drive in dynamic modes. Similarly, at kP, the sliding contact 17 is set1 | It is inserted to the left of intermediate terminal 18 with the division factor fb of the left side of the additional resistor 16 (between the output of the tachometer bridge and intermediate output 18). Thus, the proposed device with the specified choice of its pairs of meters allows to increase the accuracy of determining the load moment of the electric drive in static and dynamic modes, providing zero static and speed errors and the possibility of decreasing from less accurate acceleration the change of the moment to less than acceptable, as well as minimizing the time of the transition process with its almost monotonous nature. In addition, taking into account the magnetic flux values of the electric drive motor eliminates the influence of changes in this flux on the accuracy of determining the load torque. The proposed implementation of the EMF sensor included in the device also provides an increase in accuracy by eliminating the influence of the voltage of the motor power supply circuit on the output voltage of the EMF sensor and by ensuring the inertia of this sensor. In this case, the effect of the change in the resistance of the engine motor circuit on accuracy is significantly reduced, since, in contrast to the known. The device parameters (in the EMF sensor) are chosen not proportional to the absolute values of the parameter of this circuit, but to the difference in the ratio of the parameters of the windings of the core and additional poles, whose change is less than their absolute changes due to the proximity of the temperature regimes of these windings. Claim 1 .. A device for measuring the load torque of a direct current motor with an independent excitation winding, containing current sensors, EMF and a unit for measuring the magnetic flux of an electric motor, multiplying and summing units, the output of the current sensor is input to the multiplying unit, the EMF sensor is in the form a tachometer bridge, the shoulders of which include windings of the core and the additional poles of the engine, and two resistors, characterized in that, in order to increase accuracy, the device is equipped with a dividing unit and after Consistently included by the integration unit and the proportional-integrating dynamic unit covered by feedback, the output of the magnetic flux measurement unit is connected to the multiplication unit whose output is connected to the input of the integrated unit, the outputs of the EMF sensor and the magnetic flux measurement unit are connected to the inputs of the division unit the output is connected to the input of a proportional-integrating unit .. 2. The device according to claim 1, characterized in that the EMF sensor is equipped with a variable resistor with a sliding contact with two extreme and one intermediate pins, a decisive amplifier and three condensates, two of which are connected to the tachometer bridge resistors, and the third between the sliding contact and the intermediate terminal of the variable resistor, the extreme terminals of which are connected respectively to the output of the tachometer bridge and to the output of the soldering amplifier, and The intermediate terminal of the variable resistor is connected to the input of the decision amplifier, the output of which is connected to the input of the division unit. Sources of information taken into account in the examination 1. USSR author's certificate for application 2394586, cl. Q 01 L 3/22, 1976. 1 .. 2. Authors certificate of the USSR 420893, cl. q 01 L.3 / 22, 1972.