SU924576A1 - Method of determination of shaft rotation frequency and direction - Google Patents

Description

one

The invention relates to methods for determining phase shifts and their derivatives and can be used in the construction of automatic and computing devices.

A known method for determining the magnitude and direction of the shaft rotational speed, which consists in generating a stable frequency signal that modulates the output voltage and supply voltage of the phase shifter, isolates the voltage difference between the frequencies, compares their periods, and determines the difference from the difference and the sign. the order and direction of the speed of rotation of the shaft 1.

The disadvantage of this method is its complicated hardware implementation, due to the need to use modulators of the output and supply voltage of the phase shifter and low accuracy when measuring low rotational speeds, due to the small difference of the periods separated from the modulated voltages.

A known method for determining the magnitude and direction of the rotational speed of the shaft, based on a comparison of the periods of the supply voltage and the output voltage of the phase shifter 2.

The disadvantage of the method is that at low speeds due to the instability of the pulse fronts

To comparable stresses, the resolution and accuracy of measurements are significantly reduced, and it is also difficult to determine the direction of rotation of the shaft. Thus, the known method

15 has a narrow dynamic measurement range, which is the ratio of the Maximum speed of rotation of the shaft to the minimum measured with a given accuracy.

I

The purpose of the invention is to expand the range of measurements and increase the accuracy of measurements in the field of low speeds. The goal is achieved by forming three sequences of short pulses, the period of the first of which is equal to the period of the supply voltage, the period of the second sequence is greater than the period of the first sequence, and their difference is less than the period of the first sequence, and the period of the third sequence is equal to the period of the output voltage of the phase shifter, then determine the time interval between the moments of coincidence of the phases of the pulses of the first and second sequences and the time interval between the moments of coincidence phase pulses of the second and third series, at whose magnitude is determined rotational speed and rotational direction determined by the sign of the difference of the measured time intervals. FIG. 1 shows time diagrams of a sequence of short pulses; in fig. 2 is a schematic diagram of a device implementing a method for determining the magnitude and direction of the speed of rotation of a shaft. A method for determining the magnitude and direction of the rotational speed of the shaft pea is inserted as follows. From the voltage supplying the phase shifter, two sequences of short pulses are formed (Figures 1a, 16). The first of these sequences (Fig. 16) has a period equal to the period of the voltage supply to the phase shifter. The second sequence is obtained from the first by increasing the pulse repetition period by an AT value equal to a part of the second sequence period (Fig. 1a). The time interval between the moments of coincidence of the phases of the pulses of the second and first sequences is determined. In this case, the coincidence of the phases of the pulses occurs at a time interval ti determined from the relations:

(one)

t, P (T - AT); t, (T -AT), (2)

P is the number of pulses of the first sequence, passed from coincidence to the next coincidence of the phases of the second and first sequences;

From inequality (6), it follows that the speed measurement range is determined by the periods T and AT. As follows from the relations () and (5), the rate of change of the voltage phase with the phase shifter uniquely determines the duration of the time interval t and tj, which can be selected T - period of the second sequence; AT is the difference between the periods of the second and first sequences. It should be noted that the coincidence of the pulses of the second and first sequences occurs on condition that the period T of the second sequence contains an integer n differences AT of the durations of the periods of the second and first sequences. The voltage removed from the phase shifter is generated in the form of short pulses shifting relative to the second sequence with a speed cJ to the left. Thus, a third sequence is formed (figure 1c), the phase of the pulses of which coincides with the phase of the pulses of the second sequence at a time interval t determined from the relations: T pLT + oita; (3) tn (T - AT) (4) When rotated to the right, the time interval between the moments of coincidence of the phases of the second and third formed sequences is determined by the relation T - lt where t, is the time interval between the two closest moments of coincidence of the phases of the second and third b formed sequences when moving to the right. It follows from relation (5) that it has a physical meaning when the inequality of type 5 is fulfilled necessary to provide the required measurement accuracy at the minimum rate of change of the voltage phase with the phase shifter. To determine the direction of rotation, we compare the time intervals between the moments of coincidence of the phases of the second and first sequences and the second and third sequences, when the condition tj t is satisfied, the movement is left, and if t is provided, the movement is right, where t2 and t are the time intervals between the moments of phase coincidence The second and third sequences to it. It is obvious that the angle of rotation of the shaft H and the phase shift oL of the voltage pulses from the phase shifter are related by the relation -K. (T) where K is the coefficient for converting the angle of rotation of the shaft of the phase shifter to the phase shift of the voltage pulses from the phase shifter. Consequently, the rate of change of the phase shift of the voltage pulses from the phase shifter is related to the rotational speed of the shaft of the phase shifter with the relation –– NR K (S) Taking into account (8), the time interval between the moments of coincidence of the phases of the pulses of the second and third sequences is written as AT T – DT (9) it follows that the specified time interval — tjjj uniquely determines the rotational speed of the shaft of the phase shifter. The device implementing the method comprises: a power supply unit 1 for the phase shifter, a phase shifter 2, short pulse shapers, frequency divider 6, owls 7 and 8 circuits, drops, trigger 9, frequency multiplier 10, valve 11, counter 12, frequency dividers 13 and It frequency two, valves 15 and 16, reversible counter 17 The output of power supply unit 1 is connected to the inputs of the phase shifter 2 and the formers of 3 and A, and the output of the phase shifter through the driver 5 is connected to one input of the matching circuit 7 whose second input is connected to 6 with the second input of the matching circuit 8 and with a divider 6 frequency output, in D of which is connected to the output of the driver 3, and the first input of the matching circuit 8 is connected to the output of the driver k, the outputs of the matching circuit 7 and 8 are connected to the inputs of the trigger 9, the output of which is connected to the controlled input of the valve 1 1, the output of which is connected to the counter 12, and the control input of the valve 11 is connected to the control inputs of the valves 15 and 16 and to the output of the frequency multiplier 10, the input of which is connected to the power supply unit of the phase shifter, the outputs of the circuit 7 and 8 match through the frequency dividers 13 and k to two inputs of gates 15 and 1b, in passages which are connected respectively to negative and positive inputs of a reversible counter (PC) 17. The apparatus operates as follows. From the voltage of the unit 1, which supplies the phase shifter 2, with the help of the formers 3 and form two sequences of infinitely short pulses, the periods of which are different in the DT, simultaneously with the help of the imaging unit 5 a sequence of short pulses is formed, the phase of which varies with speed -. At the moment of coincidence of the second pulse arriving from the generator 4 of the sequences, the coincidence circuit 8 generates a pulse, tilting trigger 9, which opens a valve 11, transmitting high-frequency pulses from the multiplier 10 to the counter 12, when the pulses of the second and third sequences coincide, the coincidence circuit 7 produces a pulse, setting the trigger 9 to the initial state, wherein the trigger closes the key 11 and in the counter 12 a code equal to the time interval t2J is recorded which uniquely determines the rotational speed no. Then the cycle is repeated. The rotational speed is determined as follows: the pulses from scheme 7 and 8 of coincidence are divided into two dividers 13 and I, the keys 15 and li6 are opened between these pulses from the outputs of the dividers

on + and - the inputs of the PC 17 are pulses from the multiplier 10, the sign of the difference at the output of the reversing counter 1 corresponds to the direction of speed + to the left, - to the right.

Claims (2)

1. Author's certificate of the USSR 20 No. 525025, cl. G 01.P., 1976. 2. USSR author's certificate №, cl. G 08 C 9/03, 1970 (prototype).