Benefit Factor

The benefit factor metric therefore provides a mechanism for ascertaining the most efficient architecture in terms of electrical power employed against improvement in acceleration performance. This represents an innovation as, whilst providing a drivetrain solution that has maximum performance, utilising too much additional extra electrical power is likely to result in a drivetrain that is both expensive and costly and unlikely to be commercially viable.

14.5.3 Process Innovation

The process that led to the design of the hybrid drivetrain was also innovative. Unlike other hybrid vehicles in motorsport, the design process did not use the regulations of a given race series as a starting point, but used the overall requirements of the system, gathered in an academic and rigorous fashion. This resulted in a solution that met both the technical and commercial requirements of the system. This is important for the club motorsport industry which, unlike the professional motorsport sector, relies on selling vehicles to members of the public.

The design process, consisting of four phases, each phase having three steps, the completion of which will lead to a deliverable, is shown in Figure 54. The activities that were carried out in each step are shown in Table 41. After each phase of the process there was an output that was used to aid the design of the drivetrain throughout the rest of the project. The outputs for each stage are shown in Table 42, the along with the output found during the project.

Phase 1 – Requirements Analysis Company Motorsport and Road Requirements Analysis Customer Requirements Analysis Conjoint Analysis and Market Simulation Tool

Deliverable 1 – Design Target

Phase 2 – Architecture Selection

Identification of Viable Architectures Vehicle Simulation Tool Architecture Selection and Benefit Factor Calculation

Deliverable 2 – Architecture Choice

Phase 3 – Component Specification

Motor Selection Energy Storage System Selection and Testing System Control Concept

Deliverable 1 – High Level Design

Step Activity Company, Motorsport and

Road requirements Analysis

Determination or company, road and motorsport requirements

Customer Requirements Analysis

Customer survey to understand identify key requirements Conjoint Analysis and Market

Simulation Tool

Conjoint analysis to understand complex customer requirements and tool to simulate price points of different configurations

Identification of Viable Architectures

Analysis of available architecture options

Vehicle Simulation Tool Development of a tool to simulate the performance of the vehicle

Architecture Selection and Benefit Factor Calculation

Use of simulation tool to compare different architectures and analysis using benefit factor calculation

Motor Selection Use of simulation tool to compare the effect of different motors

Energy Storage System Selection and Testing

Selection of energy storage system and testing of selected system

System Control Concept Design of system control concept based on requirements and energy storage system

Mechanical and Electrical Design

Design and packaging of the system within the vehicle System Integration Design of the control system and integration with the

existing vehicle

Testing Testing of the vehicle against the requirements Table 41. Design Process Steps

Phase Output Project Output

Phase 1 Design Target 0-60 mph acceleration time of 3 seconds Phase 2 Architecture Choice Through-the-road parallel hybrid architecture

Phase 3 High Level Design Lithium ion battery, dual motor drive with set boosts Phase 4 Prototype Vehicle Hybrid Westfield

Table 42. Design Process Phase Outputs

The main difference between this process and a process followed for other forms of motorsport is the work involved in Phase 1, Phase 2 and Phase 3. For example, in Formula One the regulations have predetermined the deliverables for Phase 1, Phase 2 and the System Control Concept step in Phase 3. Formula Hybrid allows more flexibility, but the system requirements found in Phase 1 have been predetermined by the regulations and the scoring structure.

It is worth noting the significance of the Benefit Factor calculations in the process. If there are no regulations to follow, in the interest of achieving increased performance, excessive hybridisation could occur. The new Benefit Factors calculation provides a method of

restricting excessive hybridisation, resulting in a system more likely to meet the cost and complexity requirements.

The use of conjoint analysis, a first for this industry, showed that the tendency of vehicle manufacturers to primarily quote engine power figures may not be the best use of the vehicle attributes in the club motorsport market. With a closer relationship to driver enjoyment, 0 to 26.8ms-1 (0-60mph) acceleration was shown to be of higher importance and became the design target deliverable from Phase 1.

Following this process through, allowed an innovative hybrid drivetrain to be developed that met both the commercial requirements of the industry and the technical requirements. Without this process, it may have been tempting to develop a hybrid drivetrain based on that used in other forms of motorsport. This would have resulted in a drivetrain that was not innovative and not optimised for the club motorsport industry.

There is also scope to extend the use of this process out of club motorsport and into other forms of motorsport. To do this would require the deregulation of hybrid electric vehicles in these other forms of motorsport to allow vehicle manufacturers to develop their own innovative drivetrains. This would allow the process to further the development of hybrid electric vehicles in motorsport sectors, other than club motorsport.

Furthermore, the process could be used to develop innovative hybrid vehicles in the wider niche vehicle industry and the mainstream automotive industry. Whilst the current focus for the design of most road going vehicles is the reduction of CO2 output, many vehicles

operating in the niche vehicle industry (and the mainstream automotive industry to some extent) are not as concerned with this requirement. Following this process, ensuring that the system requirements are well understood and followed, could result in new and innovative hybrid drivetrains being developed.

customer survey and conjoint analysis, carried out as part of this Engineering Doctorate, were used to develop the business case for this car. The vehicle simulation tool, also designed as part of this Engineering Doctorate, was then used to analyse the design options available. As a result of its use on the hybrid prototype, the iRacer uses the same Oxford YASA Motors dual motor system and the hybrid vehicle. The iRacer now had its own vehicle class in the EV Cup electric vehicle race series, with a small fleet of road going vehicles also under fleet test.

15 CONCLUSIONS

The aim of this project was to develop an innovative hybrid electric vehicle drivetrain suitable for use in club motorsport. Through a process of requirements analysis, simulation, testing and design, a hybrid electric drivetrain was successfully integrated into a Westfield Sportscars Sport Turbo vehicle, resulting in the build of the first hybrid electric vehicle designed for club motorsport. The main findings of the project are:

• Customers in the club motorsport industry are receptive to alternative drivetrains as

long as they produce an increase in driver enjoyment, with almost no preference shown for conventional petrol drivetrains over hybrid petrol drivetrains.

• A through-the-road parallel hybrid architecture provides the greatest benefit to a

club motorsport vehicle, in terms of 0 to 26.8ms-1 (0-60mph) time decrease and electric power utilised.

• High power lithium-ion battery systems provide a better mix of specific power and

specific energy then ultracapacitor systems for club motorsport applications.

• It is possible to package a hybrid drivetrain, capable of achieving a 0 to 26.8ms-1

(0-60mph) acceleration time of less than four seconds, within the chassis constraints of a club motorsport vehicle, in this case a Westfield Sportscars Sport Turbo.

• The cost of producing a hybrid electric drivetrain for use in club motorsport market

is not cost prohibitive.

• A drivetrain that enables the advantages of four wheel drive to be realised in club

motorsport through the use of a through-the-road parallel hybrid architecture.

• A ‘shelf engineered’ hybrid system that could be used on other platforms owned by

Potenza Sports Cars as well as other platforms in the niche vehicle industry.

• A driver control system that allows the hybrid drivetrain to drive through gear

changes, whilst leaving the driver in control. It is important that this level of driver control is retained in hybrid drivetrains in the club motorsport and niche vehicle industry.

• A system operation by where the driver of the race car is given a set amount of

energy for a given race and is able to decide how and when the energy is used in the form of short boots. This has application in both the club motorsport sector as well as the wider motorsport industry.

• A process that makes use of a lack of predefined requirements, in the form of

technical regulations, to determine the optimum hybrid electric vehicle design for a given type of motorsport and niche vehicle. This process makes use of innovations in conjoint analysis and Benefit Factor

• The use of conjoint analysis to fully understand the customer requirements and

enable the creation of a design target that will meet these requirements.

• The use of the Benefit Factor calculation to ensure that the designs for hybrid

electric vehicles for motorsport and the niche vehicle industry make the most efficient use of additional electric power.

15.1 Future Work

This project has been successful in proving the concept of a hybrid electric vehicle for use in club motorsport and in being innovative within the motorsport industry. However, further work is required to take the prototype through additional testing and into production.

15.1.1 Inverters

Due to the failure of the inverters originally used, further work should be carried out with alternative inverters. Initial tests could be carried out using half of the existing battery system to ensure that the battery voltage is within the inverter operating range. If

successful, a redesign of the inverter integration and of the battery pack would be necessary to enable full dynamic testing of the prototype.

15.1.2 Dynamic Testing

With the inverters working correctly and safely, full dynamic testing of the prototype vehicle could be continued. The aim of this testing would be to test the function of the system, refine the integration and control of the system. It would also include dynamic testing to prove the acceleration of the vehicle and the effects of the hybrid drivetrain in a racing situation.