外文翻譯--公共接地?zé)o刷直流電機(jī)驅(qū)動(dòng)系統(tǒng)的fpga實(shí)現(xiàn)(編輯修改稿)
2024-09-18 17:13 本頁(yè)面
【文章內(nèi)容簡(jiǎn)介】 f PWM_ON control signalsThe electromagnetic torque of electrical machine can be expressed with (5):Te =(eaia+ebib+ecic) (5)Where, Te represents electromagnetic torque, p is pole pairs, ωrepresents electrical rotating speed, ea ,eb and ec represent phase back electromotive force, ia, ib and ic represent phase current.When electrical machine operates conventional control scheme and neglects influence of phase conversion, the electromagnetic torque of electrical machine can be expressed as (6):Te=2pkei (6)Where, ke represents electromagnetic time coefficient, i is current of steady state.In order to describe the torque ripple of phase conversion causing by PWM_ON modulation, this paper will take period [60176。, 120176。] for example to deduce it.Three phase currents showed in(7)can be obtained according the mathematical model of BLDCM.ia(t)=i(2ke+2Rsi+DU)tib(t)= （DUke）t (7)ic(t)=i+(4ke+3Rsi+DU)tWhere, U is bus voltage, D is duty cycle of PWM.According to (5) and (7), the electromagnetic torque of BLDCM system with PWM_ON modulation can be described by (8):Te=2pkei +[2UDt8ket6Rsit] (8)The ripple of electromagnetic torque can be expressed as:ΔTeT=[8ket+6Rsit 2UDt] (9)From (9), it is definite that the ripple of electromagnetic torque is determined by ω and D. So the minimal ripple of electromagnetic torque can be got in suitable condition of ω and D.B. Commongrounded drive schemeThe optical coupler drive scheme is most widespread used at present. The sampled current, speed and position signals transmit to the control part through optical couplers, and then the output signals pass through the optical coupler again and are amplified by drive part, last control the switches of the inverter. Isolation scheme is showed in . Optical coupler used in the system can cause time delay, even using high speed optical coupler the time delay is more than 2us. At the same time, because not every optical coupler has the same characteristic, the control signals can not be synchronous. Thus, the performance of system bees worse. In this paper, mongrounded drive scheme is proposed. Optical couplers are not used between control part and drive part. Then time delay is reduced, so the dynamic and steady response characteristics of system are improved, and system cost is reduced. The mongrounded closed loop system is shown in . The transfer function of system can be described as (10). Block Diagram of isolating drive Block diagram of mongrounded drive F(S) = (10)Where, G(s) is the open loop transfer function. The drive system shown in Fig 3 can be described by transfer function (11)FG(S) = (11)Where, T1, T2 is the time delay in the main channel and feedback channel respectively. Contrast of step response between mongrounded drive and isolating driveSimulate the system according to (10) and (11) when both T1 and T2 are 2us. Simulation waveform is shown in Fig 5. Thus, system has better performance if the mon ground strategy is used.Using both PWM_ON modulation and mongrounded drive scheme in the BLDCM system will reduce torque ripple, time delay, system fault and cost and so on.IV. PWM_ON COMMONGROUNDED BLDCM SYSTEMThis part introduces the digital achievement of the proposed scheme based on FPGA chip. Digital BLDCM system consists of FPGA
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