Improvement of Ride Comfort of Turning Electric Vehicle Using Optimal Speed Control Yingyi Zhou, Tohru Kawabe Abstract—With the spread of EVs (electric Vehicles), the ride comfort has been gaining a lot of attention. The inﬂuence of the lateral acceleration is important for the improvement of ride comfort of EVs as well as the longitudinal acceleration, especially upon turning of the vehicle. Therefore, this paper proposes a practical optimal speed control method to greatly improve the ride comfort in the vehicle turning situation. For consturcting this method, effective criteria that can appropriately evaluate deterioration of ride comfort is derived. The method can reduce the inﬂuence of both the longitudinal and the lateral speed changes for providing a confortable ride. From several simulation results, we can see the fact that the method can prevent aggravation of the ride comfort by suppressing the inﬂuence of longitudinal speed change in the turning situation. Hence, the effectiveness of the method is recognized. Keywords—Electric vehicle, speed control, ride comfort, optimal control theory, driving support system. I. I NTRODUCTION I N this century, internal-combustion engine vehicles (ICEVs) have been widely spread all over the world. Consequently, the environmental problems are going seriously. One of the key solution of this problem is the development of electric vehicles (EVs). EVs have several good points compared with the ICEVs [1]-[4]. For examples, • Environmentally friendly. EVs emit no tailpipe pollutants and no air pollutants. • Energy efﬁcient. Electric motors much better convert the energy to power than internal-combustion engine. • The input/output response of electric motors is 2 orders magnitude faster than that of internal-combustion engine. • The accurate magnitude of torque generated by electric motors can be detected. • The small size car can be realized by using multiple motors placed in each wheels. From these advantages, EVs can realize the driving with excellent ride comfort by adequate speed control. The ride comfort is important to prevent a motion sickness and an accident. Many researches about the relation of vibration and ride comfort have been done [5]-[7], [14]. However, these are studied about the ride quality referred by the vertical vibration. But, the longitudinal acceleration/deceleration or tuning motion are also affect to the ride comfort. Therefore, in this paper, to improve the ride comfort during vehicle turning, we proposes new optimal speed control Y. Zhou is with Honda Motor China Technology Co., Ltd., Guangdong, 510530 China. T. Kawabe iswith the Division of Information Engineering, Faculty of Engineering, Information and Systems University of Tsukuba, Tsukuba 305-8573 Japan (phone: +81-29-853-5448; e-mail: kawabe @cs.tsukuba.a.jp). method. In this method, the inﬂuence of lateral speed change is considered as well as the inﬂuence of longitudinal speed change by using the evaluation index based on longitudinal acceleration, longitudinal jerk and lateral acceleration. The simulations show that the proposed method is effective for the improvement of ride comfort. II. EVALUATION OF RIDE COMFORT Since various factors have an inﬂuence on ride comfort, the evaluation criteria of ride comfort is generally depend on the sense of individuals. There are several research about the evaluation of the ride comfort with respect to the frequency of vibrations in vertical and horizontal directions about railroad carriage [8]. But, most of these research investigated the ride quality with respect to the sustained vertical vibration of the steady run. But it is important to evaluate the ride comfort with respect to lateral speed change. From this point of view, [9], [10] have investigated the relation between the acceleration/deceleration, the jerk (time derivative of the acceleration) and ride quality. In [9], [10], subjectivity evaluation of the ride comfort tests on a start, a stop, immediate start, a run situations including the hitting the brakes for the resting posture and the reading posture. Then, the linear multiple regression model about the ride comfort index as follows is derived. d 1 (t ) = β 0 + β 1 a p+ (t )+ β 2 a p− (t )+ β 3 j r+ (t ) +β 4 j r− (t )+ ε (t ) (1) where a p+ (t ), a p− (t ), j r+ (t ), j r− (t ) in T =(t − 3, t ) are given as follows. a p+ (t )=  max t ∈T a(t ), (|max t ∈T a(t )|≥|min t ∈T a(t )|) 0, (|max t ∈T a(t )| < |min t ∈T a(t )|) (2) a p− (t )=  0, (|max t ∈T a(t )|≥|min t ∈T a(t )|) min t ∈T a(t ), (|max t ∈T a(t )| < |min t ∈T a(t )|) (3) j r+ (t )=  1 3  t t −3 j 2 (τ )d τ , ( ¯ j(T ) ≥ 0) 0, ( ¯ j(T ) < 0) (4) j r− (t )=  0, ( ¯ j(T ) ≥ 0)  1 3  t t −3 j 2 (τ )d τ , ( ¯ j(T ) < 0) (5) And where parameters in (1) are deﬁned in Table I. Since d 1 (t ) is the index at the speciﬁc time t calculated from the acceleration and the jerk in the real time, we can not derive the World Academy of Science, Engineering and Technology International Journal of Electrical and Information Engineering Vol:12, No:9, 2018 541 International Scholarly and Scientific Research & Innovation 12(9) 2018 scholar.waset.org/1307-6892/10009364 International Science Index, Electrical and Information Engineering Vol:12, No:9, 2018 waset.org/Publication/10009364