True dynamic capability designed into test cells

Ricardo took the decision to invest in a transmission and driveline test facility to simulate the dynamic behaviour of a complete driveline and transmission system as though it were on a real road

Ricardo took the decision to invest in a state-of-the-art transmission and driveline test facility to simulate the dynamic behaviour of a complete driveline and transmission system as though it were in a real vehicle on a real road.

The low inertia machines, which can be programmed with actual or simulated road load data, feature electrical motors with a high transient response that are capable of changing speed at a rate of 12,500 rpm per second for the two-wheel drive rig and 6,850 rpm per second for the all-wheel drive rig.

This acceleration is faster even than a high revving Formula 1 engine can deliver.

More significantly perhaps is that the rigs are designed to create the prodigious levels of torque produced by the latest generation of diesel engines both in light commercial vehicles as well as high performance executive saloons..

The new rigs can test the complete driveline of a wide range of vehicles including passenger and sports cars, light commercial and off-highway vehicles.

The 450Nm of torque input for the two-wheel drive rig, for example, is considered to be equivalent to the traction limit in first gear of a front-wheel drive rally car.

High performance rear-wheel drive cars can also be tested on the two-wheel drive rig but for higher torque capacity the four-wheel drive rig can operate in two-wheel drive mode as well.

Ricardo can employ the rigs at the very early stage of a project if data is required to substantiate the selection of concept drivelines.

It can use the rigs during the development phase to calibrate shift systems and to develop new algorithms for differential control systems.

It can also validate entire drivelines in an accelerated manner by condensing the duty cycle down to the most damaging transients in a representative test that is closest to real world environments.

One of the major benefits of Ricardo's test cells is their ability to be programmed with real road load data, which is used to accelerate 'key life testing' of transmissions and drivelines.

Until now such tests would have to be carried out as part of the durability testing of prototype vehicles at a proving ground, which is both expensive and time consuming.

Alternatively, conventional transmission test rigs lack the transient capability to reproduce the loads dynamically imposed in a driven vehicle.

The Ricardo test cells however have this unique ability to realistically mimic such conditions.

Moreover, by compressing road load data it is possible to concentrate on the dynamic loads likely to do the most damage to the transmission and driveline, thus reducing the overall duration of the test.

Ricardo therefore can test validate a transmission and driveline design in less time than it would normally take, under precisely controlled conditions, which can be accurately reproduced time and time again, and without incurring the major cost of building a prototype or mule vehicle.

Moreover, as designers of driveline and transmission systems, Ricardo engineers have an expert knowledge of the duty cycles of each component and an understanding of how design can best be test validated for production.

This total capability means that Ricardo can develop new driveline systems for clients with an unparalleled level of confidence.

The Schenck-Ricardo T2000 control system is highly sophisticated enabling each rig to imitate all load conditions including moving rapidly from one type of surface to another thereby simulating a swift changeover from surfaces with the highest to the lowest coefficient of friction, including up to the point where a wheel lifts off the ground.

Moving back and forth between dry tarmac and black ice each rig can mimic for example intense rally conditions.

Similarly, the loadings of off-highway vehicles under extreme conditions can also be faithfully reproduced.

The control software is an iteration of the code written for Ricardo's Advanced Engine Development Centre at Shoreham in West Sussex.

The major difference being the significant increase in complexity from controlling one electrical machine employed for an engine dynamometer to three electrical machines used for the two-wheel drive transmission rig and five electrical machines used for the four-wheel drive rig.

Moreover, the rig control system has to provide a combination of speed and torque control modes for both input and output electrical machines dependent on whether a clutch is engaged or disengaged and whether the transmission is in or out of gear.

Controlling both speed and torque under dynamically changing conditions for all different types of transmission and driveline was the major challenge facing the Ricardo software development team.

Initially, the facility comprises two-wheel and four-wheel drive rigs.

Depending on future client requirements Ricardo has the space to accommodate four additional test cells.

Specification of both test cells is impressive.

The input motor for the four-wheel drive rig delivers its maximum torque of 1,000Nm at 4,900rpm and has a maximum power rating of 513kW (685bhp).

Its maximum speed rating is equivalent to an engine revving to 6,500rpm.

The four output absorbers can each handle a maximum torque of 4,000Nm at 500rpm and have a maximum power rating of 210 kW (280bhp).

The maximum speed rating of 2,500 rpm is equivalent to a velocity of approximately 280kph (175mph) in a vehicle with a nominal saloon-sized 600mm (2ft) diameter wheel and tyre.

The input motor for the two-wheel drive rig delivers its maximum torque of 450Nm at 4,600rpm and has a maximum power rating of 217kW (290bhp).

Its maximum speed rating is equivalent to an engine revving to 9,000rpm.

The two output absorbers can each handle a maximum torque of 3,000Nm at 500rpm and have a maximum power rating of 157kW (210bhp).

The top speed rating of 2,500 rpm is the same as that for the four-wheel drive rig again equivalent to a road speed in a car of approximately 280kph (175mph).

Each rig features a mounting arrangement, which is representative of the engine interface.

From that point onwards the transmission and driveline is as it would be in the vehicle all the way through to the actual wheel hubs, which are mounted to the output absorbers.

For manual transmissions the clutch and gearshift actuation is fully robotised.

For both two-wheel and four-wheel drive rigs, the drive unit from the input motor is adjustable through 90 degrees to accommodate in-line as well as transverse engine transmission configurations.

Additionally, the four-wheel drive rig can be configured to accommodate all possible driveline layouts.

The decision to build a four-wheel drive rig was based on the extra functionality it provides and the need to accommodate the increasing trend towards all-wheel drive vehicles.

A key driver for Ricardo's investment in its new test cells is the marketing advantage that carmakers can now derive by carefully engineering driveline and transmission characteristics.

Potential benefits range from enhanced fuel economy, emissions, safety and performance right through to NVH refinement as well as influence upon vehicle ride and handling.

Increasingly vehicle drivelines are being used for product differentiation and for defining a car's all-important marque values.

And with increased platform sharing and common vehicle architectures the importance of differentiating the brand is becoming ever more significant.

Another motivation has been the increasing trend for carmakers to outsource complete programmes requiring a turnkey solution from early design concepts all the way through to initial production.

Ricardo's consultancy work for clients covers every type of advanced transmission and the company is active in all new technologies related to drivelines.

This includes next-generation power-shifted automated manual transmissions (AMTs) and continuously variable transmissions (CVTs) as well as complex hybrid powertrains.

The new test cells have the flexibility to handle a wide range of driveline and transmission systems.

Already, Ricardo has invited both customers and competitors to review its test facility.

"If you are worried about showing what you know today, it suggests you haven't really got much confidence in where you are going to be in the future," says Gerald Andrews, managing director, Ricardo Driveline and Transmission Systems.

"If a competitor comes to look at our test rigs now, by the time they have them up and running we will still be two years ahead.".

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