The Kiira EV powertrain employs a simple battery electric vehicle powertrain consisting of an Energy storage bank, energy converter and a rotary machine (induction motor). It is powered by electricity which is stored in the in the battery bank through repetitive charging. The battery system of the Kiira EV consists of Lithium-ion batteries with very high energy storage capabilities, high charge acceptance, high specific power and high energy density. The battery system banking is unique consisting of 4 battery banks of 64 cells connected in series. The banking ensures energy system modularity for effective battery monitoring, safety, increased reliability and maintenance. The battery bank capacity of 40 AH and 207 V is engineered to achieve an inter-charge distance 80 km, a requirement for a commuter student vehicle on Makerere University campus. The battery is protected through an intelligent battery management system which monitors and controls individual cell temperatures for maximum cell safety. Each cell has sensor on PCB plate which monitors the individual cell temperatures, voltages and currents for effective power utilization from each individual cell. The battery energy restoration system (charging) is unique in implementation because battery charge restoration will be achieved from any wall socket at home which is readily available in the city center. This negates the need for new charging infrastructure.
The Front wheel drive power transmission layout was adopted so as to achieve maximum torque transmission, elimination of additional components like the propeller shaft, reduction of mechanical power losses and to also create ample space at rear for components including the battery charger, baggage and spare tire.
The Vehicle ‘engine’ consists of a controller and motor. An induction motor has been used because it is very efficient compared to other motor types and its rigidity and torque output performance likens it to the conventional internal combustion engine. Motor control is achieved through an efficient Vector control algorithm for effective power switching from the inverter. The inverter utilizes intelligent power modules for three phases switching to the motor. Driver communication of commands to the motor controller is through a distributed communication network implemented using the CAN protocol
The Kiira electric vehicle incorporates a real time control and communication network. This network serves to control both the car environment and safety of the passengers. It also provides real time information to the driver regarding the state of every Drive train subsystem. For the technicians the onboard display system provides a diagnostic system that has a heuristic algorithm and is therefore easy to use. It provides guidelines for location of faults and also documents how the faults can be rectified. The algorithms in the distributed system have been designed to accommodate and adjust to the conditions of our local environment, so the system is an all-weather system. The Kiira EV employs drive by wire and has a very high responsiveness, this means it can gain top speeds within very short times. The control system has been designed as a resilient system, which means that it is adaptive to failure of some of its components. For the less critical system, if the operation fails to be performed using one way it will try to use another path to effect this operation an example can be if the indicators malfunction and the driver flips the left turn switch, the Lighting node inspects the indicators, if it finds an open circuit then it will use the break light to inform the other road users that the car is turning left.
The Acers chassis is a mechanical structure that bears the car load and on to which all other components like the engine, suspensions, frame etc. are connected. In simple terms it can referred to as the vehicle skeleton. The Kiira EV chassis is unique in design and fabrication/ implementation .There are quite a number of chassis types that have been used in different automobiles including; the ladder (mostly used in heavy duty cars), monologue (not so specific), tubular space frame (specifically made for rally cars), tubular chassis and the backbone chassis type. The KIIRA chassis design takes into consideration loading and stress requirements during acceleration and deceleration events. Two thick plates running across the length of the car with angle bars placed across the width of the car take care of acceleration and deceleration force loads ,torsional forces in case of humps and pot holes plus side impacts. The implementation/fabrication has employed simple technologies of arc welding and MIG welding achieving a unique cruciform format chassis
Unlike conventional automobiles which employ anybody fabrication of the chassis and frame, The Kiira EV consists of a frame work of round cross-section tubes to offer resistance to impact forces from any direction hence protection of the car in-mates. This also serves the purpose of raising a super-frame. This is the outer shell of the car that maps out the car’s shape and defines the extents of the car i.e. the car’s length, width and height. The Kiira body was designed to achieve maximum cabin space, best aerodynamics performance and aesthetics. The Kiira EV body has been fabricated out of the light weight fiber glass material through simple tooling techniques .It consists of a super-frame built around standard parts like the windscreen, doors, etc. using small bars (4mm) to form webs for strength purposes. Before the final body finish, a wire mesh super frame was laid onto the web of small bars to narrow down the sinking space frames/ windows for glass fiber compound (Isopon P.40). The hardened and smooth finish of the body is made out of a mixture of Isopon P.40 fiber glass compound and Dibenzoylperoxide compounds as a hardener which when dry is sanded to achieve the a final finish of light weight but strong body .
The strategic goal of the vehicle design project is to incubate a Centre for Research in transportation technologies with a vision of presenting a wholesome solution to the transportation needs in Uganda. In the follow up to the Kiira EV we intend to design and fabricate a 28-seater commuter electric vehicle KAYOOLA a Green Public Transport Solution tailored for Kampala City .
Kiira EV Design Specifications
|Number of Doors||3|
|Top Speed||100 Km/hr|
|Wheel Base||2175 mm|
|Ground Clearance||200 mm|
|Dry Weight||1000 Kg|
|Motor Type||Induction Motor|
|Motor Power||20kW/26 Hp|
|Maximum Power||47 kw/62 Hp|
|Maximum Battery Voltage fully charged||256 V|
|Battery Voltage fully discharged||180 V|
|Maximum Theoritical Speed||100 Km/hr|
|Charging time at 13 A 240 V||5 Hours|
|Power Consumed Per Charge||15.6 kWh|
|Cost of Charging (UGX 385 Per Unit)||6000 UGX|
|Maximum motor Speed||10,000 rpm|