Abstract: Introduced one kind as the master control chip new electrically operated bicycle velocity modulation control system’s design proposal 煾 left system’s hardware constitution and the software design method take AVR monolithic integrated circuit ATmega8. The experiment proved: This system performance is reliable, the cost is low, is one kind practical not brushes the direct current motor velocity modulation system.
Key word: ATmega8; Not brushes the direct current motor; Velocity modulation control system
1 introduction
Presently, along with the protection environment, the frugal energy’s call grows to ever greater heights 熚 ga 廴⒛What purine disposition was jasmine pure the new transportation vehicle to arouse people’s universal interest, simultaneously also obtained the enormous development, the electrically operated bicycle was one of them 煟 fort 牎 K the electrical energy which sent out by the accumulator cell takes the actuation energy, made the power by the electric motor, had the non-waste gas pollution, “zero emissions”, not to have the noise, facilely artistic and so on characteristic 熖 tuo osprey excrement obviously Shen Si to reproach in the rosy cloud in the big or media-sized cities to use. But in the present market’s electrically operated bicycle also has some insufficient consummations the place, particularly the motor control aspect waits for further enhances. This article according to not brushes direct current machine’s principle, in 2002 promoted section of new AVR using American Atmel Corporation upscale monolithic integrated circuit ATmega8 to take the master control chip to design one kind not to brush the direct current machine velocity modulation control system, this system had the hardware architecture to be simple, the software design nimble, the suitable surface was broad, merit 熅 shen good fortune happy ǖ neon and so on low in price washed the eyebrow gully to be negligent
2 ATmega8 chip synopsis
The ATmega series monolithic integrated circuit has carried on the characteristic which in the AVR series AT90 has and increased the more interface functions moreover in the province electric properties, the stability, the anti-jamming and the flexible aspect is completer and is perfect. ATmega8 belongs to a ATmega series monolithic integrated circuit (ATmega16/ATmega32/ATmega64/ATmega128) subset, its interior integrated the large capacity memory and the rich hardware interface electric circuit, and can support the C higher order language and the assembly language effectively on the software.
ATmega8 is one section uses the low power loss CMOS craft production based on AVR RISC (simplification set of instructions) the structure 8 monolithic integrated circuits. The AVR monolithic integrated circuit’s core is 32 working registers and the rich set of instructions connects in together, all working register with ALU (arithmetic logic unit) direct connected, may simultaneously visit (read-write) in a clock cycle with an instruction 2 independent registers. This kind of structure may raise the code efficiency, causes the majority of instructions the execution time is only a clock cycle, therefore may achieve near 1MIPS/MHz performance, the running rate is higher than compared to the ordinary monolithic integrated circuit 10 times. The ATmega8 main performance characteristic is as follows:
(1) high performance, low power loss 8 AVR micro controller. Uses the advanced RISC simplification set of instructions structure; Some 130 function formidable instruction, majority is the monocycle instruction; Contains 32 8 general working registers; Work when 16MHz the command processing speed is 16MIPS.
(2) internal integrated the large capacity non-volatility procedure and the data-carrier storage. 8k the byte Flash program memory may scratch writes the number of times to be bigger than 10000 times; 512 byte E2PROM scratches writes the number of times to be possible to reach 100000 times at least; Supports online programs (ISP) and programs (IAP) in the application; Has the programmable procedure to add the mil.
(3) rich formidable exterior connection. Has 2 belt pre-frequency division 8 fixed time/counters, 1 belt pre-frequency division 16 fixed time/counters; 3 PWM the channel 熆 soil moisture order I the long-tailed monkey guarantees Duan Huiyue to know by heart the bridle slow to push the taxi silly jian mold school to wish the pulse-duration modulation output; 6 channel A/D transformation; A I2C serial interface, a programmable USART connection, support main/from the SPI synchronization serial interface which, receives/sends; In track shoe RC oscillator’s programmable watch-dog timer; Internal simulation comparator.
(4) has the special micro controller performance. The content may control on electricity replacement delay circuit and programmable owes the voltage examination electric circuit; The chip interior and exterior altogether has 18 interrupt sources; 5 kind of dormancy patterns (free time, ADC noise abatement, province electricity, power failure, standby).
3 system hardware designs
The overall system mainly includes the rotor position examination electric circuit, to measure that the fast electric circuit, the velocity modulation electric circuit, the MOSFET entire bridge electric circuit, the current limiting electric circuit and so on, shown in Figure 1 is its functional block diagram. And not brushes the direct current machine by the electric motor main body, the rotor position sensor and the electronic switching electric circuit three parts is composed. The direct-current power supply through the switching circuit to the electric motor stator winding power supply, the position sensor may momentarily examine rotor’s position, and controls switching valve’s breakover and the closure according to rotor’s position signal, thus realizes the electronic commutation.
3.1 rotor position examination electric circuit
In this design not brushes the direct current motor to have 2 pair of magnetic pole 煻 ㄗ You Puduan to take sprouts the connection 煟 to pull wo the stern position transducer’s spatial spacing for 60° 熂 to blow xiang inlays, no matter what 120°. 3 Hall sensor’s output H1, H2, the H3 distinction receives ATmega8 directly 26, 27, 28 feet, utilizes these three foot’s digital-analog conversion function (ADC) to be possible to carry on the sampling and the transformation to the Hall signal.
3.2 electrical machinery speed control electric circuit
a. measures the fast electric circuit
Must to not brush direct current motor’s rotational speed to carry on the accurate control 熓 purple to thread a needle surveys its rotational speed accurately. This design reflects electric motor’s rotational speed using the rotor position transducer’s output pulse signal. First position transducer signal after sampling recuperation electric circuit songzhi monolithic integrated circuit’s PD3 foot 煾 waste foot may take the exterior interrupt source the input port. chen receives the signal impulse unceasingly along with electric motor’s rotation 煟 school mold. When PD3 receives to a rise along will start timer T0 to start to time, until receives until the next neighboring rise along, the timer T0 time result is the time which the electric motor rotates needs 熅 sui thinks of the pure cedar to throw the worried thoughts bao duo machine rotational speed.
Figure 3
b. commutation velocity modulation electric circuit
Not brushes the direct current motor rotational speed the control method to be possible to divide into each kind of limit which the excitation control method and armature voltage control method two kind of 煟 chu 牎 S takes sui rat-a-tat receives to be many, and the exciting coil inductance is big 煻 condition the response to be bad. What therefore is commonly used is changes the armature terminal voltage to realize the velocity modulation armature voltage control method. Supposes the direct-current power supply voltage is Ud, connects resistance R for the armature to connect in parallel fashion to power source Ud, then armature both sides’ voltage Ua is Ua=Ud-IaR, obviously 煹 gu the interrogation deep attachment daimei tortoiseshell one sieved purely seeks wei said that Miao Geng 煷yong served the velocity modulation purpose. But this tradition’s accent presses the velocity modulation method efficiency to be low. 煶 you to reads aloud ji cao mediocre male li sigh Miao Gu刂 along with the electric power electronic technology’s development the pepper ā# school to wish stops 熉 cui Miao mao wearily 牼 to shed looks at the washing with watercolors brother one, its basic principle as shown in Figure 2.
Supposes adds in the electrical machinery armature both sides rectangular wave peak-to-peak value voltage is the Ud 熢 horsefly black armature both sides voltage mean value is
Ua=(T1-T2)Ud/(T1 T2)=(2T1/T2-1) Ud= (2α-1) Ud
And Alpha is the dutyfactor, may achieve through the change Alpha value adjusts the pressure the goal. As a result of 0 ≤α≤1, the Ua value’s scope is - Ud~ Ud, thus the electrical machinery may, the counter-two direction velocity modulation revolution.
Shown in Figure 3 is one kind of electrically operated bicycle not brushes the direct current machine velocity modulation system’s partial schematic diagrams. Through the chart in the monolithic integrated circuit may on the sampling electrically operated bicycle handle the adjustable resistance voltage, passes through after again A/D transforms, delivers the PWM register, thus controls monolithic integrated circuit’s PB1 foot, output dutyfactor adjustable PWM signal. This signal and from current limiting electric circuit LM358 comparator’s output signal together through software comparison, in the current limiting electric circuit does not work in the situation outputs the PWM signal, coordinates the software control PB0, PD5 and the PD6 pin actuates the corresponding light pair, then controls the MOSFET entire bridge electric circuit phase change breakover, realizes electrical machinery’s commutation. Therefore, through the adjustment monolithic integrated circuit PWM signal’s dutyfactor, may change finally adds on the electric motor stator winding’s voltage, thus realizes electric motor’s velocity modulation.
4 system software controls
ATmega8 can support the C language and the assembly language effectively on the software. The C language present has become designs embedded system’s standard language, it both has the ordinary higher order language structurization programming, the readability to be good, maintenance convenient characteristic, and has the assembly and so on low-level language to be convenient visit to hardware, code efficiency high characteristic. This design is realizes with the C language programming, has the very good probability, its program flow diagram as shown in Figure 4.
5 concluding remark
Has obtained the good tendency, the static characteristic with this project design’s electrically operated bicycle velocity modulation control system in the experiment movement process. The high performance-to-price ratio ATmega8 monolithic integrated circuit’s utilization reduced the cost greatly, enhanced the software design flexibility, has enriched the hardware interface function, has created the good condition for the next system upgrade.
