Control Co-Design: An engineering game changer

Although the demand of battery electric vehicle (BEV) growths fast as the requirement of reducing greenhouse gas emission and the usage of fossil fuels, the limited driving range and unfriendly retail price present barriers to BEV to provide comparable performance as a traditional vehicle. This paper proposes a dual-motor two-speed direct drive BEV powertrain to boost average motor operational efficiency in daily driving without increasing any complexity of manufacturing or control, ultimately, saving limited battery energy and manufacturing cost. The specifications of the proposed powertrain are first identified through mathematical and graphical calculations, which split traditional one propelling motor to two with separate permanent engaged gears to maximize the motor efficiency. Based on dynamic powertrain modeling in a Simulink/Simscape, economic shifting strategy, and dynamic torque transfer control are designed and tested. According to the simulation results, it is noticed that significant energy efficiency improvement can be achieved. Thanks to the optimized torque transfer control strategy, extremely low vehicle jerk are recorded during the shifting process. At last, conclusions can be made that the proposed dual-motor powertrain superior to the traditional single motor counterpart in terms of fuel economy, driving range, and cost.

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A Novel Dual-Motor Two-Speed Direct Drive Battery Electric Vehicle Drivetrain

This paper deals with the speed synchronization control of a connected vehicle subject to a replay attack. A large number of replay attack signals are injected into controller area network (CAN) through external network, which greatly reduces the real-time control performance of a connected integrated motor-transmission (IMT) system. In order to ensure the performance of an IMT speed tracking system under large random message delays, a robust reset controller combined with a delay-robust speed synchronization controller satisfying energy-to-peak performance is designed in this paper. The uncertain impact caused by a replay attack is described by large random network delays which are modeled by polytopic inclusion. Then, a dynamic output-feedback controller considering the uncertainty caused by attack-delays is proposed for online speed tracking. Moreover, a robust reset controller is designed to obtain comparatively better transient response in the case of large attack-delays. In this control strategy, once the reset condition is triggered, the after-reset value calculated by linear matrix inequalities (LMIs) would replace the dynamic state vector. Finally, the effectiveness of the proposed controller is verified by comparing it with model predictive control (MPC), existing PD control considering delays and energy-to-peak robust control in terms of performance.

Robust Reset Speed Synchronization Control for an Integrated Motor-Transmission Powertrain System of a Connected Vehicle Under a Replay Attack

In this paper, a four-wheel electric braking system configuration is proposed for electric vehicles and its braking performance is compared with other conventional braking system configurations at different initial vehicle speeds and different road conditions in the case of emergency braking. In order to make the vehicle wheel slip ratio track the optimal slip ratio, a control method that combines sliding mode control and extended state observer is designed. Neural-network sliding mode control is designed for the driver’s braking command tracking in the normal braking condition. In order to improve braking energy recovery, a new braking torque distribution strategy is developed for the proposed four-wheel electric braking system based on the motor characteristics and vehicle dynamics. The designed braking torque distribution strategy is able to improve the energy recovery by adjusting the braking torque distribution ratio between the front and rear wheel braking torque while tracking the driver’s braking command. Numerical simulations have been conducted and the simulation results show that although the braking performance of the four-wheel electric braking system is worse than the conventional braking system at high initial braking speed, it still is able to meet the vehicle braking international standards and simplifies the braking system structure and saves cost. The proposed braking torque distribution strategy can improve energy recovery efficiency compared with the average allocation strategy and deceleration based allocation strategy. The simulation results show that the four-wheel electric braking system configuration with the proposed braking torque distribution strategy is suitable for low to medium speed light electric vehicles.

Four-Wheel Electric Braking System Configuration With New Braking Torque Distribution Strategy for Improving Energy Recovery Efficiency

To improve the observation accuracy and robustness of the sensorless control of an interior permanent magnet synchronous motor (IPMSM), a sliding mode observer based on the super twisting algorithm (STA-SMO) with adaptive parameters estimation control is proposed, as parameter mismatches are considered. First, the conventional sliding mode observer (CSMO) is analyzed. The conventional exponential approach law produces a large chattering phenomenon in the back EMF estimation, which causes a large observation error when filtering the chattering through the low-pass filter. Second, a high-order approach law of the super twisting algorithm is introduced to observe the rotor position and speed estimation, which uses the integral function to eliminate the chattering of the sliding mode. Third, an adaptive parameter estimation control (APEC) is presented to enhance the observation accuracy caused by parameter mismatches; the motor parameter adaptive law of the APEC is designed by Lyapunov’s stability law. Finally, the proposed method not only reduces both the chattering and the low-pass filter, but it also enhances accuracy and robustness against parameter mismatches, as discussed through simulations and experiments.

Sliding Mode Observer with Adaptive Parameter Estimation for Sensorless Control of IPMSM

This paper deals with the speed synchronization controller design for networked integrated motor-transmission (IMT) powertrains via controller area network (CAN). It is well known that, in current implementations, CAN has been widely used in the control system design of automotive powertrains. However, on the other hand, the application of CAN would not only lead to network-induced delays but also bring about protocol constrains, e.g., data package capability and utilization ratio limitation, which would deteriorate the system and make the controller design a challenging problem. This paper is to provide a co-design methodology that can cope with all these problems and ensure satisfactory control effect for the speed synchronization control of IMT powertrain systems. First, a networked IMT powertrain system using CAN as underlying network is presented and the dynamic model for the speed synchronization control is derived. Second, the network-induced delay model is introduced and improved considering data packet capability and utilization ratio limitation. The control-orient discrete-time model is also derived based on the improved delay model. Third, a co-design methodology using sliding mode controller and offline priority scheduling based on Lyapunov stability criterion is proposed. The results of simulations and tests show the effectiveness of the proposed co-design methodology.

Speed Synchronization Control for Integrated Automotive Motor-Transmission Powertrains Over CAN Through a Co-Design Methodology

All-wheel-independent-drive electric vehicles (AWID-EVs) have considerable advantages in terms of energy optimization, drivability and driving safety due to the remarkable actuation flexibility of electric motors. However, in their current implementations, various real-time data in the vehicle control system are exchanged via a controller area network (CAN), which causes network congestion and network-induced delays. These problems could lead to systemic instability and make the system integration difficult. The goal of this paper is to provide a design methodology that can cope with all these challenges for the lateral motion control of AWID-EVs. Firstly, a continuous-time model of an AWID-EV is derived. Then an expression for determining upper and lower bounds on the delays caused by CAN is presented and with which a discrete-time model of the closed-loop CAN system is derived. An expression on the bandwidth utilization is introduced as well. Thirdly, a co-design based scheme combining a period-dependent linear quadratic regulator (LQR) and a dynamic period scheduler is designed for the resulting model and the stability criterion is also derived. The results of simulations and hard-in-loop (HIL) experiments show that the proposed methodology can effectively guarantee the stability of the vehicle lateral motion control while obviously declining the network congestion.

Co-Design Based Lateral Motion Control of All-Wheel-Independent-Drive Electric Vehicles with Network Congestion

An accelerated second-order super-twisting sliding mode observer with an adaptive gain is proposed for a typical nonlinear system. The key contribution of this algorithm is that the rate of convergence of observation error is accelerated remarkably by introducing “system damping.” Chattering issue is attenuated with a satisfactory performance compared with conventional sliding mode observer. Furthermore, adaptive gain can vary with deviation between the trajectory and the sliding mode switching manifold dynamically so that overshoot can be reduced. The novel observer is proven mathematically to be convergent in a finite time. Finally, an example of nonlinear system is given to verify the performance.

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Accelerated Adaptive Second Order Super-Twisting Sliding Mode Observer

As there is no clutch or hydraulic torque converter in electric vehicles to buffer and absorb torsional vibrations. Oscillation will occur in electric vehicle drivetrains when drivers tip in/out or are shifting. In order to improve vehicle response to transients, reduce vehicle jerk and reduce wear of drivetrain parts, torque step changes should be avoided. This article mainly focuses on drivetrain oscillations caused by torque interruption for shifting in a Motor-Transmission Integrated System. It takes advantage of the motor responsiveness, an optimal active control method is presented to reduce oscillations by adjusting motor torque output dynamically. A rear-wheel-drive electric vehicle with a two gear automated manual transmission is considered to set up dynamic differential equations based on Newton’s law of motion. By linearization of the affine system, a joint genetic algorithm and linear quadratic regulator method is applied to calculate the real optimal motor torque. In order to improve immediacy of the control system, time consuming optimization process of parameters is completed off-line. The active control system is tested in AMEsim® and limitation of motor external characteristics are considered. The results demonstrate that, compared with the open-loop system, the proposed algorithm can reduce motion oscillation to a satisfied extent when unloading torque for shifting.

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Off-Line Optimization Based Active Control of Torsional Oscillation for Electric Vehicle Drivetrain

This paper deals with the speed synchronization control of integrated motor–transmission (IMT) powertrain systems in pure electric vehicles (EVs) over a controller area network (CAN) subject to both network-induced delays and network congestion. A CAN has advantages over point-to-point communication; however, it imposes network-induced delays and network congestion into the control system, which can deteriorate the shifting quality and make system integration difficult. This paper presents a co-design scheme combining active period scheduling and discrete-time slip mode control (SMC) to deal with both network-induced delays and network congestion of the CAN, which improves the speed synchronization control for high shifting quality and prevents network congestion for the system’s integration. The results of simulations and hardware-in-loop experiments show the effectiveness of the proposed scheme, which can ensure satisfactory speed synchronization performance while significantly reducing the network’s utilization.

Cheng Lin

Papers

Speed Synchronization Control for Integrated Automotive Motor-Transmission Powertrains Over CAN Through a Co-Design Methodology

Co-Design Based Lateral Motion Control of All-Wheel-Independent-Drive Electric Vehicles with Network Congestion

Accelerated Adaptive Second Order Super-Twisting Sliding Mode Observer

Off-Line Optimization Based Active Control of Torsional Oscillation for Electric Vehicle Drivetrain

Speed Synchronization Control of Integrated Motor–Transmission Powertrain over CAN through Active Period-Scheduling Approach