Design consideration and optimization for an eco-friendly hybrid car system using mechanical advantages of the multi-input epicyclic gear

Rapid advancement in green technology and sustainable engineering has led to global and public awareness of greenhouse effect. The significantly advancing automotive industry and the ever increasing number of road vehicles powered by internal combustion engines fuelled with petroleum are causing problems such as global warming, air quality deterioration, and depletion of fossil fuel; a scarce natural resource. Unless effective countermeasures are taken, the world will soon be uncomfortable to live in or even worst, inhabitable due to the unpredictably changing climate as a side effect of global warming. A newly designed 3-degree-of-freedom (DOF) electromechanical transmission and an optimal power control approach in power sharing between an IC engine and two electric motors for complex hybrid vehicle will be described thoroughly in this thesis. The concept electromechanical transmission design has four ports that allows for 3 inputs; TWO Motor’s and ONE IC engine. The mechanical concept of the system is realized by employing the three degrees of freedom (DOF) twin epicyclic gear train with specially selected gear ratios to satisfy an optimal power sharing strategy. The first stage of the train provides high torque from the IC engine and moderate torque from Motor 1. The second stage provides high speed with lower torque from Motor 2. Motor 1 is a source of moderate electromagnetic torque and speed to drive the wheels while Motor 2 is selected to drive the wheels with highest speed but minimum torque. Such arrangement of power sources is achieved by careful selection of all the gear ratios in the drive train. The closed-loop controller has been designed to provide a proper switching sequence between Motor 1, Motor 2, and IC engine. The IC engine in the design is engaged into the transmission when necessary by means of clutch and is selected to charge the battery via an additional motor/generator to maintain charge level of the batteries at the nominal level most of the time. The motor/generator is also utilized as a starter for the IC engine. Motor 1 is selected to start driving the vehicle at rest and is used to run the vehicle most of the time when driving around in urban roads. When the vehicle’s torque demand increases beyond Motor 1’s capability, the controller engages the IC engine into the transmission to deliver higher torque. Conversely, when the vehicle’s speed demand increases beyond Motor 1’s capability, the controller activates Motor 2 to deliver more speed. In other words, this transmission design emphasizes on optimized operation for IC engine in high torque output region with minimal fuel consumption and an electric motor dedicated for maintaining high speed cruising and low torque driving conditions. The velocity ratios for the transmission in each section are carefully selected so as to balance between speed and torque yet maintaining drivability in urban and highway roads. The designed electromechanical transmission design and optimized hybrid engine drive control system are able to minimize the power usage of the IC engine which in turn minimizes exhaust gas emission, greenhouse gases, and saves cost on petrol usage as compared to conventional vehicles. It also provides a wide range of torque and speed values to drive the vehicle. The simulation of the newly developed dynamic models of the driven vehicle has been conducted using MATLAB Simulating tools and then discussed in this thesis to prove the feasibility of the developed system and suitability for a vehicle driver.