The Horsepower Reserve Formulation of Driveability for a Vehicle Fitted With a Continuously Variable Transmission

• Published in: Vehicle system dynamics Vol. 41; no. 3; pp. 157 - 180
• Main Authors: Smith, Michael Henry, Barth, Eric J., Sadegh, Nader, Vachtsevanos, George J.
• Format: Journal Article
• Language: English
• Published: Colchester Taylor & Francis Group 01.01.2004; Taylor & Francis
• Subjects: Applied sciences; Exact sciences and technology; Machine components; Mechanical engineering. Machine design; Springs and dampers; Vehicle driving; Optimal trajectory; Fuel economy; Fuel consumption; Continuously variable drive; Motor fuel consumption; Objective function; Brake; Constrained optimization
• ISSN: 0042-3114; 1744-5159
• DOI: 10.1076/vesd.41.3.157.26514

Summary A systematic methodology is developed for choosing the optimum ratio trajectory of a continuously variable transmission in a passenger vehicle. The optimum CVT ratio schedule is formulated as a constrained optimization problem with maximum fuel economy as the objective function and driveability concerns and physical limitations included as the constraints. The key notion to achieving good driveability is the introduction and definition of a horsepower reserve function that creates a consistent and desirable vehicle response under different driving conditions. Simulation results compare the optimized schedule's performance with several other possible ratio schedules, including the minimum brake specific fuel consumption map. Results from the optimized schedule indicate only a mild tradeoff between driveability and fuel economy relative to the other ratio schedules. The ratio optimization problem formulation and solution provide a novel and unique approach for systematically addressing driveability and fuel economy considerations associated with a continuously variable transmission.