Abstract: According to the SRM principle of work, has designed based on DSP56F805 three-phase (6/4) the SRM double closed loop driving system. Has analyzed one three-phase SRM starting technique, used the integral to the speed and the electric current link to separate the PI control algorithm and the increase type PID control algorithm separately. The reasonable hardware source use and the good control software design, causes SRM to move stably reliable, the interphase current profile is improved.
Key word: SRM; DSP56F805; Starting; The integral separates PI; Increase type PID
0. introduction
Switch magnetic resistance electrical machinery SRM (Switched Reluctance Motor) is the typical integration of machinery system, has the structure to be simple, the movement is reliable, the efficiency is high and cost low status prominent merit. This article selected Motorola Corporation to develop uses in the motor control 16 fixed-point DSP chip DSP56F805 designing three-phase (6/4) the SRM double closed loop driving system specially. This chip instruction execute speed is quick, the fruitful in resources, has provided the reliable information processing and the control for the high performance switch magnetic resistance electrical machinery’s control.
1.SRM driving system’s description
The SRM driving system mainly by SRM, the controller, the power transformer, the position detector set and the electric current detector set and so on is composed. This article designs the switch magnetic resistance motor-driven system uses the speed electric current double closed loop the control mode, its system structure diagram as shown in Figure 1.
The position detector set carries on the examination to the SRM rotor position, provides the basis for the random time rotor’s velocity calculation and the phase change logical control. The electric current detector set uses in examining electrical machinery’s interphase current, realizes to the electrical machinery interphase current control. The controller must realize the function includes: Completes the rotor velocity calculation and the definite breakover according to rotor’s positional information; According to the rotational speed deviation, completes speed ring’s control using the speed regulator; Reference current value which and feedback interphase current value deviation outputs according to the speed regulator, completes the electric current link’s control through the current regulator; Reference current value which and actual rotational speed situation outputs according to the speed regulator, through angle control determination corresponding clear angle and shutdown angle; Completes the commutation logical control according to the rotor positional information; Through the PWM generator to power transformer output logic level pulse-duration modulation signal PWM. Actuates electrical machinery’s rotation through the power transformer.
Figure 1 SRM velocity modulation system’s structure diagram
2. control circuit hardware part design
The control circuit acts according to the external input, synthesis processing electrical machinery feedback signals and so on rotor position, electric current, voltage and temperature, through the analysis computation, sends out the PWM control signal according to certain control policy to the power transformer, controls electrical machinery’s revolution. At the same time, this electric circuit also has pressed with protection functions and so on excess temperature. As core control circuit hardware structure drawing as shown in Figure 2 take DSP56F805.
Figure 2 control circuit hardware architecture diagram
The keyboard signal from the DSP56F805 GPIO mouth introduction, realizes the rotational speed through the keyboard operation, to change, hypotheses and so on temperature and voltage. The numerical code demonstrated that actuates through the SPI mouth, to use in demonstrating information and so on electrical machinery rotational speed. Carry on a/d conversion the interphase current, the voltage and the temperature signal input to the ADC module, satisfies the control the need. Orthogonal decoder’s PHASEA0, PHASEA1 and PHASEB0 catch three group Hall position transducer’s jump separately along the signal, with calculates the electrical machinery rotational speed as well as the gain rotor positional information. At the same time, these sensor signal is also introduced to 3 GPIO mouths, the control chip may also through inquire these 3 mouth level gain rotor positional information. DSP56F805 chip pulse-duration modulation module PWMA produces six group PWM square-wave signal. And, PWMA0~PWMA2 control power transformer high-end 3 IGBT, its output’s PWM profile the current regulator output signal’s control, through is changed the PWM profile the dutyfactor to realize the electrical machinery rotational speed adjustment; PWMA3~PWMA5 control power transformer low end’s 3 IGBT, it outputs the PWM profile to clear the shutdown angle and the rotor positional information control, realizes logic reverse control. Realizes the motor-driven system and the superior machine communication through the SCI mouth.
3. control system’s realization
3.1 position examinations and speed estimate
The system uses 3 Hall sensors to carry on the position examination. These 3 sensors are separated 120. , when the electrical machinery rotor rotates the inductance most main point, the corresponding Hall sensor produces on jumps along, indicated that the rotor and the stator arrive aline the position. Thus, 3 group square-wave signal period which outputs from 3 Hall sensors is 90. , and the phase difference is 15. (as shown in Figure 3). DSP56F805 through orthogonal decoder’s PHASEA0, PHASEB0 and PHASEA1 catches these three group sensor signal jump along; At the same time, may also through the inquiry corresponding three GPIO mouth level, gain the rotor positional information.
Figure 3 three group Hall sensor output signal
In the electrical machinery normal work’s process, establishes the DSP56F805 capture module for under jumps along triggering, when Hall sensor output signal’s under jumps along the arrival, DSP56805 has a capture interrupt, neighboring 2 times interrupts the time-gap through the read, may calculate electrical machinery’s actual rotational speed. If neighboring 2 times interrupts the time-gap is, then electrical machinery’s rotational speed is:
= (r/min)
3.2 startings and phase change
When the electrical machinery starts, if the initial breakover judges contains errors, will cause the electrical machinery to present the reverse, will create the electrical machinery revolution the disorder. Therefore, when initial point, the electrical machinery breakover correct judgment is a key question which the present paper first needs to solve.
When the electrical machinery is in static, the controller through reads three group Hall sensor’s condition gain electrical machinery rotor positional information. May see from Figure 3, when gains from three group Hall sensors when the positional information respectively is “110″, “101″ and “011″, in 15. In the mechanical angle scope, corresponding C, B and a inductance is at the ascent stage separately. In this case, only need give corresponding C, B or A electrifies can have the request starting moment, the starting effect is good.
When gains from the sensor when the positional information is “100″, “010″ and “001″, in 15. In the mechanical angle corresponds the inductance is not the constant rise. When the positional information is “100″, because because a inductance was at the downward phase to have negative torque, the B inductance start section in this mechanical angular region between the inductance invariable existence zero torque situation, the C inductance the inductance invariable also has zero torque liquidation phase in this mechanical angular region between the situation. If only gives B or C electrifies the starting effect not to be good. Therefore, must give B and C two is the same time electrifies. When likewise, the positional information is “010″ must give A and C two is the same time electrifies; When the positional information is “001″ must give A and B two is the same electrifies.
If the electrical machinery is the single-phase circular telegram starts, establishes DSP56F805 the capture functional module jumps for under after triggering, the electrical machinery by the starting condition directly enters the running status, starts the normal phase change. When the electrical machinery is two are the same the circular telegram starts, first will catch the functional module to establish for on jumps along triggering. In electrical machinery start-up procedure, if a sensor output signal produces on jumps along, closes A, B maintains a circular telegram; If the B sensor output signal produces jumps along, closes B, A maintains a circular telegram; If the C sensor output signal produces jumps along, closes C, B maintains a circular telegram. When changes over to a breakover after two breakover startings, will catch the functional module to establish for under jumps along triggering, the electrical machinery enters the running status by the starting condition, starts the normal phase change.
In electrical machinery normal phase change process, if under the sensor output signal produces jumps along, the DSP56F805 capture module will have the capture interrupt, in capture interrupt definite breakover, will complete the commutation logic the control.
3.3 interphase current examinations
Through the string enters a diverter in the interphase current electric circuit, above obtains the loss of voltage to realize the interphase current examination. In the sampling resistance’s loss of voltage enlarges after the filter inputs to the DSP56F805 ADC module. What because in the system uses to the power switch’s control is cuts the single-valve the way, the interphase current is not has been able from the sampling resistance to measure that only then, in the high and low two power switch opens the time which or closes only then may in the sampling resistance obtain. Therefore, the electric current sampling must with the PWM frequency synchronism. At the same time, establishes the electric current zero spot in ADC transformation scope half place, enables in the sampling resistance the positive and negative loss of voltage to examine.
3.4. control policy and control algorithm realization
The SRM speed control is realizes through the speed regulator and the current regulator. Considered the integral link to the greatly over retardance, to enable the system to have the quick response, serially connects an integral separation switch in the speed ring return route, uses the integral separation to the speed ring the PI control algorithm. Uses the increase type PID control algorithm to the electric current link.
Based on electric current link’s value of exports CMP, carries on the establishment to the DSP56F805 PWM module’s corresponding register, then may from PWM the module output dutyfactor invariable PWM profile, thus realizes to power transformer high-end 3 IGBT carries on the control.
4. conclusion
This article take electrical machinery special-purpose chip DSP56F805 as the core, the success has realized the SRM speed electric current double closed-loop control. In the article author’s innovation spot was while proposed one kind of simple suitable three-phase SRM starting technique’s, used the integral to the speed ring and the electric current link to separate the PI control algorithm and the increase type PID control algorithm separately, the electrical machinery starting ability is good, the interphase current profile had the good improvement. Figure 4 has given the electrical machinery starts when the speed profile. And, chart a is the speed and the electric current link uses when the PID control the speed profile, chart b is uses when this article algorithm the speed profile. May see from the chart, when the speed and the electric current link selects the PID method over big, the speed of response is slow, the system control time is long, but uses time the control mode which this article proposed the over obvious reduction, the speed responds quickly.
a) the speed and the electric current link uses when PID speed profile
b) uses when this article algorithm speed profile
Figure 4 toggle speed profile
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