• Title/Summary/Keyword: Metal belt CVT

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Transfer Function Derivation and LQG/LTR Speed Ratio Control for a Metal Belt CVT (금속벨트 CVT의 전달함수 도출과 변속비 LQG/LTR 제어)

  • 김종준;송한림;김현수
    • Transactions of the Korean Society of Automotive Engineers
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    • v.5 no.1
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    • pp.49-58
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    • 1997
  • In this paper, a transfer function was obtained for a PWM high speed solenoid valve controlled metal belt CVT system. The transfer function was defined as the ratio of speed ratio to PWM duty ratio and derived in time domain by linear regression analysis from the experimental results. The transfer function obtained showed different dynamic characteristics for the up and down shift. Also, LQG/LTR controller was designed for the CVT system using the transfer function. It is seen from the experimental results that LQG/LTR control showed good performance for the speed ratio tracking and disturbance rejection. The phase difference and relatively slow response are considered due to the inaccuracy os the transfer functions, which resulted from the inherent nonlinearities of the transmission characteristics of the metal belt CVT.

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Power Transmission Characteristics and Speed Ratio-Torque Load-Axial Force Relationship for a Metal V-Belt CVT (금속 V-벨트 CVT의 동력전달 특성과 변속비-부하토크-축력 관계)

  • 김광원;김현수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.2
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    • pp.349-357
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    • 1990
  • Power transmission characteristics and speed ratio-torque load-axial force relationship for a metal V-belt CVT were investigated theoretically and experimentally. In the metal V-belt CVT drive, it was found that the power was transmitted by thrust force and that band tension should be greater than compression force between the metal blocks. The experimental results for the speed ratio-torque load-axial force relationship showed good agreement with those predicted using equations developed from theoretical considerations.

Analysis of Primary and Secondary Thrust of a Metal Belt CVT Part I : New Formula for Speed Rtio-Torque-Thrust Relationship Considering Band Tension and Block Compression (금속벨트 CVT 의 구동 및 종동 드러스트 해석 Part I : 밴드 장력과 블록 압축력을 고려한 새로운 변속비-토크-트러스트 관계식)

  • 이희라;김현수
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.8
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    • pp.132-142
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    • 1999
  • In this paper, a new formula for primary and secondary thrust of metal belt CVT is proposed considering variation of band tension, block compression and active arc for each of the primary and secondary pulleys. For the secondary thrust, effective friction coefficient is introduced considering the effect of flange deflection. Nondimensional primary and secondary thrust of the metal belt CVT by the new formula agree well with the experimental results except for low torque range, $0\;<\;{\lambda}\;<\;0.2$ at speed ration i = 1.0. The new formula can be used in design of the primary and secondary thrusts control system for the metal belt CVT.

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Low Level Control of Metal Belt CVT Considering Shift Dynamics and Ratio Valve On-Off Characteristics

  • Kim, Tal-Chol;Kim, Hyun-Soo
    • Journal of Mechanical Science and Technology
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    • v.14 no.6
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    • pp.645-654
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    • 2000
  • In this paper, low level control algorithms of a metal belt CVT are suggested. A feedforward PID control algorithm is adopted for line pressure based on a steady state relationship between the input duty and the line pressure. Experimental results show that feedforward PID control of the line pressure guarantees a fast response while reducing the pressure undershoot which may result in belt slip. For ratio control, a fuzzy logic is suggested by considering the CVT shift dynamics and on-off characteristics of the ratio control valve. It is found from experimental results that a desired speed ratio can be achieved at steady state in spite of the fluctuating primary pressure. It is expected that the low level control algorithms for the line pressure and speed ratio suggested in this study can be implemented in a prototype CVT.

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Analysis of belt behavior for a metal V-belt CVT (금속 V-벨트 CVT의 벨트거동 해석)

  • 김현수;이재신
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.2
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    • pp.557-566
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    • 1991
  • The metal V-belt behavior of a continuously variable transmission was investigated analytically and experimentally. Numerical results showed that nondimensional belt radial displacement increased in the radial inward direction for the driven pulley, while that of the driver pulley increased for the first 90 degrees of the active are and decreased with the increasing torque load. Experimental results for the belt radial displacement were in good agreement with the theoretical results. However, the absolute magnitude of the belt radial displacement was so small that the change in the belt displacement could not be measured in the experimental range except for the inlet region of the driven pulley, where the radial inward displacement was observed due to the effect of bending moment. The speed ratio-axial force relationship derived from the belt behavior analysis also showed god agreement with the experiment.

An Experimental Study on the Shift Characteristics of a Metal Belt Type Continuously Variable Transmission (CVT) (금속벨트식 무단변속기(CVT)의 변속특성에 관한 실험적 연구)

  • 이충섭
    • Transactions of the Korean Society of Automotive Engineers
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    • v.5 no.6
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    • pp.36-43
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    • 1997
  • To cope with quest to improve the fuel economy and vehicle performance, Continuously Variable Transmission with Changing the speed ratio between minimum and maximum ratio by infinite step, is more efficient than conventional multi-ratio transmission. In this paper, to investigate a specific CVT shift ratio diagram and CVT shift characteristics, CVT vehicle was tested on the proving ground and chassis dynamometer. The test results are as follows; CVT can obtain the excellent vehicle performance and fuel economy changing the shift ratio by infinite step, without rapid change of engine revolution and driving force. And CVT can set up a special shift range that obtains not only the engine brake effect but also the maximum speed driving.

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Control Strategy of Ratio Changing System for a Metal V-Belt CVT Adopting Primary Pressure Regulation (압력제어 방식 금속 벨트 CVT 변속비 제어 전략)

  • 최득환;김현수
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.3
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    • pp.201-208
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    • 2002
  • In this paper, the control strategy of ratio changing system for a metal belt CVT adopting primary pressure regulation is developed, and the shirting performance of pressure regulating type CVT with the suggested control strategy is investigated. The control strategy suggested in this study is composed of 2 feedback loop, one is speed ratio feedback and the other is primary pressure feedback. The pressure feedback is adopted to ensure prohibiting a belt slip during transient period in a fast downshift mode. Simulation results show that the system with suggested control strategy gives appropriate response time and tracking Performance for upshift and also gives a proper primary pressure which can prohibit the belt slip. In addition, it is fecund that the given system has an acceptable servo property in tracking the target speed ratio and robustness for the disturbance of line pressure.

Analysis of Ratio Changing Characteristics of a Metal V-Belt CVT Adopting Primary Pressure Regulation (압력제어 방식 금속 벨트 CVT 변속특성 해석)

  • 최득환;김현수
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.5
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    • pp.179-187
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    • 2001
  • In this paper, a primary pressure regulating type ratio control system is developed for a metal belt CVT, and the CVT ratio changing characteristics are investigated by simulation and experiment. The hydraulic part of the ratio control system has a simple structure with one 3-way spool valve as a main ratio control valve and one bleed type variable force solenoid as a pilot valve. The mathematical modelling of the CVT hydraulic system is derived by considering the CVT shift dynamics. Simulation results of CVT speed ratio and the primary pressure agree with the experimental results demonstrating the validity of the dynamic models. It is found from the simulation and experimental results that the response time of speed ratio and primary pressure can be shortened by increasing the ratio control valve port area, and the size of feedback orifice of ratio control valve gives a damping effect on the primary pressure oscillation.

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Comparison of speed ratio-torque load-axial force characteristics and their performance for automotive rubber and metal V-belt CVT (차량용 고무 및 금속 V-벨트 CVT의 변속비-부하토크-축력특성과 성능비교)

  • 김현수;김광원
    • Journal of the korean Society of Automotive Engineers
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    • v.12 no.3
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    • pp.9-20
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    • 1990
  • The speed ratio-torque load-axial force characteristics of a rubber V-belt (RVB) and a metal V-belt (MVB) CVT are investigated and their performances are compared. It is found that power is transmitted by tension difference in RVB, and by thrust difference in MVB. The nondimensional equations for speed ratio-torque load-axial force of RVB are exactly same as those of MVB. However, actual characteristics of axial forces of RVB and MVB are different depending on their power transmission methods. The torque capacity of MVB is 5-6 times higher than that of RVB due to MVB's higher strength, even if the required axial force of MVB CVT control is 3-4 times higher than that of RVB.

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Electronic Ratio Control of Metal Belt CVT (금속벨트 CVT 변속비 전자제어화)

  • 김달철;김현수
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.4
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    • pp.100-109
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    • 2000
  • In this paper a stepping motor drive electronic ratio control system for a metal belt CVT is suggested. The electronic ratio control system developed in this study is designed to control flow rate which is required to obtain the shift speed and to control the primary actuator pressure to maintain the desired ratio. Considering these control characterstics a fuzzy logic is used for the CVT ratio control. Using the fuzzy logic dynamic models of the ratio control system is investigated and compared with the experimental results. The experimental and simulation results show that the electronic ratio control system developed in this study can be used in CVT system for the active control of the speed ratio.

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