Hyeoun-Dong Lee

Fuzzy-logic-based torque control strategy for parallel-type hybrid electric vehicle

In a parallel-type hybrid electric vehicle (HEV), torque assisting and battery recharging control using the electric machine is the key point for efficient driving. In this paper, by adopting the decision-making property of fuzzy logic, the driving map for an HEV is made according to driving conditions. In this fuzzy logic controller, the induction machine torque command is generated from the acceleration pedal stroke and its rotational speed. To construct a proper rule base of fuzzy logic, the dynamo test and road tests for a hybrid powertrain are carried out, where the torque and the nitrogen oxides (NO/sub x/) emission characteristic of the diesel engine and the drivers driving patterns are acquired, respectively. An HEV, a city bus for shuttle service, with the proposed fuzzy-logic-based driving strategy was built and tested at a real service route. It reveals that the improved NO/sub x/ emission and better charge balance without an extra battery charger over the conventional deterministic-table-based strategy.

A new PWM strategy for common mode voltage reduction in neutral-point clamped inverter-fed AC motor drives

In this paper, the relationship between common mode voltage and switching states in neutral-point clamped (NPC) inverters is clarified, and a new pulse-width modulation (PWM) strategy for reducing the common mode voltage in NPC inverter-fed AC motor drives is proposed. Among total twenty seven switching states in NPC inverter, the proposed PWM uses only nineteen switching states that generates common mode voltage of which magnitude is same or less than one-sixth of DC bus voltage. Moreover, the proposed PWM strategy satisfies the constraint such that the output voltage vector should be changed by only one switching action. Not requiring extra hardware, the NPC inverter with the proposed PWM results in the remarkable reduction in peak-to-peak of common mode voltage, compared to two-level inverter and NPC inverter controlled by conventional PWM. The proposed PWM strategy can be easily implemented in software without degradation of control performance in AC motor drives.

Efficiency-optimized direct torque control of synchronous reluctance motor using feedback linearization

In this paper, a nonlinear controller capable of high dynamic torque regulation and efficiency optimization of the synchronous reluctance motor (SynRM) using input-output feedback linearization is proposed. The cross-coupling effects in the SynRM model and the torque nonlinearity due to the iron losses in torque-speed characteristics of the SynRM are discussed. The criterion for the efficiency optimization is also introduced and investigated. Since the proposed nonlinear controller directly regulates the torque by selecting the product of d- and q-axes torque currents as one of the output variables, the nonlinear and cross-coupling aspects between the d-and q-axes torque currents and the terminal currents can he eliminated. Hence, the linear torque-speed characteristic can be achieved. In addition, by controlling the power loss-minimizing criterion directly, the proposed controller can optimize the efficiency of the SynRM without deteriorating the dynamics performance.

Torque control strategy for a parallel-hybrid vehicle using fuzzy logic

In this paper, the fuzzy logic based torque controller for a parallel hybrid electric vehicle is proposed. This controller is realized to satisfy the control objectives; improvement on the drive ability of the vehicle, battery charge balance and reduction of NO/sub x/ emission. To construct the proper rule bases of the proposed controller, the dynamo test of the parallel driving system and the investigation on driving condition and vehicle load are carried out. Through the actual road test, it can be proved that the decision-making of this fuzzy logic controller is useful for the improvement of driving performance. The proposed fuzzy logic controller gives superior performance for nonlinear and uncertain system and has robust characteristics to disturbance such as vehicle load and road conditions.

Advanced gear-shifting and clutching strategy for a parallel-hybrid vehicle

In parallel-hybrid electric vehicles (HEVs), both the electric drive and the internal combustion engine provide driving torque to the wheels either separately or together. The electric drive also can be used as a generator to recharge the batteries when the engine produces more power than is needed to propel the vehicle. As a result of the battery peak power density requirement, the vehicle needs a multispeed transmission between the electric drive and the main differential. In addition, due to the load sharing between the two independent driving sources, a clutch to separate the internal combustion engine and electric drive from the drive shaft is also required. Because the shift quality is directly related to the driving comfort of the vehicle, it is important to reduce both shift shock and time. To enhance the shift quality, we have proposed the advanced gear-shifting and clutching strategy for a parallel-hybrid drive train with an automated manual transmission (AMT). By using the electronically controlled AMT, users can achieve the optimal gear shifting, with regard to the efficiency of the hybrid drive train. Owing to the speed control of the induction machine and the diesel engine at gear shifting, the synchronization is always guaranteed and it reduces the shift shock and shortens the shift time. The dynamo-based experiments have been carried out for the purpose of proving the validity of the proposed transmission and clutch control in parallel-hybrid drive trains.

A common mode voltage reduction in boost rectifier/inverter system by shifting active voltage vector in a control period

This paper proposes a new space-vector pulse width modulation (SVPWM) strategy that can reduce the number of common mode voltage pulses in a three-phase boost rectifier/inverter system using a synchronized switching sequence. In the proposed SVPWM strategy, it is possible to eliminate one common mode voltage pulse in every control period by shifting the active voltage vectors of the inverter to align to those of the boost rectifier. Thus, a reduction in the total number of common mode voltage pulses and RMS motor leakage current can be obtained without extra hardware. Since the proposed SVPWM strategy can be simply implemented in software, it is widely applicable regardless of the power capacity of the converter and results in no increment of converter volume, weight and price. Moreover, because the proposed SVPWM strategy maintains the magnitude of the active voltage vector required for motor control and simply changes the distribution of the zero, voltage vector, it does not effect the control performance of the power converter.

Common mode voltage reduction method modifying the distribution of zero voltage vector in PWM converter/inverter system

This paper proposes a new space-vector pulsewidth modulation strategy that can restrict the common mode voltage within one-third of the DC bus voltage in a PWM converter/inverter system with the synchronization of the switching sequence. In this paper, the generation of the common mode voltage pulse whose magnitude reaches two-thirds of DC bus voltage is investigated and elimination of this voltage pulse is presented. The proposed method can be easily implemented in software and requires no extra hardware without degradation in control performance of PWM converter/inverter fed AC motor drives.

Torque control strategy for a parallel hybrid vehicle using fuzzy logic

In this paper, the fuzzy logic based torque controller for a parallel hybrid electric vehicle is proposed. This controller is realized to satisfy the control objectives; improvement on the drive ability of the vehicle, battery charge balance and reduction of NO/sub x/ emission. To construct the proper rule bases of the proposed controller, the dynamo test of the parallel driving system and the investigation on driving condition and vehicle load are carried out. Through the actual road test, it can be proved that the decision-making of this fuzzy logic controller is useful for the improvement of driving performance. The proposed fuzzy logic controller gives superior performance for nonlinear and uncertain system and has robust characteristics to disturbance such as vehicle load and road conditions.

Advanced gear shifting and clutching strategy for parallel hybrid vehicle with automated manual transmission

In this study, the advanced gear shifting and clutching strategy for parallel hybrid electric vehicle with automated manual transmission (AMT) is proposed. The efficient gear shift point considering the fuel consumption of a diesel engine and the efficiency of induction machine can be determined by means of optimization technique, and automatic gear shift can be realized by controlling the AMT. Performing the speed control of the induction machine and the diesel engine, the synchronization at gear shift is guaranteed and it enables reduction of the shift shock and shortens the shifting time. Hence, it results in the improvement of shift quality and the driving comfort of the vehicle. Dynamo-based experiments are carried out to prove the validity of the proposed transmission control strategy.

A common-mode voltage reduction in converter-inverter system by shifting active space vector in a sampling period

This paper proposes an advanced PWM method that can reduce the common-mode voltage in three-phase PWM converter-inverter systems. By the proper distribution of the zero-voltage vector of the inverter, it is possible to cancel out a common-mode voltage pulse in one control period. Since the proposed PWM method maintains the active voltage vector, it does not affect the control performance of the converter-inverter system. Without any additional hardware, the overall common-mode voltage can be decreased by one-third theoretically, compared with a conventional symmetric PWM scheme.