The transmission benchmarking process developed by Ricardo comprises of a comprehensive list of technical areas, within which Ricardo has a World-class offering.
Design and Functionality Review
The design and functionality review is a comprehensive process based on a meticulous strip-down of all components and sub-assemblies, all of which are photographed in order to provide a record of the assessment. The weight, dimensions and critical design details of each component of special interest are recorded, including gears, clutches, torque converters and actuator systems. Within this activity a detailed durability review can also be undertaken in order to determine its effective life for given modes of application. This includes integrated shaft and bearing analysis using the Ricardo software SABR and GEAR.
Hydraulic System Reverse Engineering
In order to fully understand the design and control strategy, the hydraulic system is reverse engineered and a schematic of the circuit generated for all operating conditions. Full system functionality is described covering torque converter, clutch and piston actuation techniques and protective measures. In addition, limp-home modes are evaluated in case of TCU failure. This area is becoming a key area of investigation, as control systems become more advanced and complex to meet the ever-higher expectations of automated transmission performance.
Control Strategy Reverse Engineering
The analysis of the control strategy and shift schedule (or ratio control in the case of CVT) is heavily dependent upon the design and configuration of the transmission. Shift maps (both driver selectable and where possible, adaptive) are investigated and the characteristics of the shift pattern under a range of extreme conditions assessed. Also assessed are key performance indicators and also the presence of adaptive strategies for hill, brake assist and sporty driving adaption. The results for all testing are explained clearly by the use of graphs, labelled where necessary, and accompanied by concise descriptions of the characteristic under investigation.
To enable the successful reverse engineering of the control strategy of a transmission the vehicle CAN bus data is obtained during the objective testing phase of the work using Ricardo’s CAN variable identification tool. This yields signals that the Transmission Control Unit (TCU) is accessing in it’s control algorithms, essential in modern mechatronic transmissions. (The TCU is typically embedded in the transmission and signals are not readily accessible without CAN bus access).
Subjective Transmission/Vehicle Evaluation
From the vehicle assessment conducted during a Transmission Benchmarking study a Driver Response Matrix (DRM) is generated. This is comprised from measurements of vehicle accelerative response to a comprehensive range of changes in driver demand from incremental initial vehicle speeds. The surface response generated is matched to subjective assessments carried out by Ricardo experts for the performance of the transmission. This is completed in terms of launch, shift quality and other customer perceptible operational characteristics.
Driveability, Emissions and Fuel Economy
One further aspect of the transmission benchmarking process is the assessment of driveability, emissions and fuel economy performance of the vehicle. A Ricardo vehicle emissions test facility is used to evaluate vehicle performance over standard European homologation cycles, and an assessment of the appropriateness of the control strategy made in terms of emissions and fuel consumption. A full assessment of driveability is made including the mapping of torque against engine speed and throttle angle. Using standard Ricardo CAE tools, such as a generic vehicle assessment model, the transmission is compared with other possible solutions within the same vehicle.
Efficiency Testing
Efficiency testing is carried out on a transmission rig to determine the values of efficiency for each gear (or fixed ratio) within the full range of input conditions that the transmission can operate. Performance in no-load conditions is also assessed in order to demonstrate the effect of speed on transmission efficiency. Measurements are taken of input and output speeds and torques, as well as of oil temperature, and the results of this work are expressed in terms of input conditions, power losses and efficiency. In addition to the rig tests, an analytical process is used to assess the contribution of different components and systems to overall efficiency losses. This includes clutches, seals, bearings, pumps, gears and torque converters.
Comparative Cost Evaluation
The comparative cost evaluation is an essential element of the transmission benchmarking process, enabling an understanding to be gained of the commercial viability of the design. A bill of materials is generated and directional cost estimates prepared based on different levels of production volume. This information is subsequently used in a cost-down exercise, identifying aspects of the design and manufacturing processes that could be further optimised to reduce cost.