Peugeot 3008 Hybrid4

The 3008 HYbrid4 Crossover can cover 100 kilometres on only 3.8 litres of diesel, equivalent to a CO2 output of just 99 grams per kilometre. But this economy is not achieved at the expense of performance. Together, both drives deliver 147 kilowatts (200 HP) and a full 450 Newton-metres of torque. As a result, the spacious diesel hybrid goes from zero to 100 kilometres per hour in 8.5 seconds and boasts a top speed of 191 kilometres per hour (regulated).

Switching between all-wheel, front-wheel or electric rear-wheel drive

One outstanding feature of the vehicle’s hybridisation concept is the partial all-wheel drive of the 3008 HYbrid4. In addition to the conventional front-wheel drive provided by the diesel engine, the axle-split concept developed by PSA and Bosch uses an electrically powered rear axle to provide powerful thrust. The rear axle module comprises a 27 kilowatt (37 HP) electric motor and a differential gear unit. When accelerating hard, it acts as a booster. In critical situations, it provides additional traction by activating all-wheel drive. Moreover, the torque that the electric motor exerts on the rear axle can bridge the automatic transmission’s switching pauses. In urban and stop-and-go traffic, the electric drive can also be used on its own, enabling the Peugeot 3008 HYbrid4 to run with zero emissions. Depending on the charge status of the nickel-metal hydride battery, the diesel hybrid can cover a range of about four kilometres on electric power alone. As power falls away, the diesel engine starts automatically.

The primary engine of the Peugeot 3008 HYbrid4 is the latest-generation four-cylinder 2.0-HDi turbodiesel engine with an output of 120 kilowatts (163 HP) that complies with the Euro 5 emissions standard. Its output is transferred to the front axle via an automatic six-gear transmission. With some minor modifications, the axle-split concept developed by PSA can also be used in other vehicle platforms. For example, PSA is exhibiting the new 508 RXH with HYbrid4 drive at the 2011 IAA motor show in Frankfurt, Germany.

However, the flexibility credentials of the axle-split concept go beyond its relatively easy hybridisation. Thanks to its virtually independent rear-wheel drive, the 3008 HYbrid4 crossover model is the best of both worlds. It can complete short urban journeys with zero noise and exhaust emissions – covering about four kilometres solely in electric mode. Rough terrain and snowy inclines present no problem for the vehicle either, thanks to its elegant all-wheel drive capability. And its efficient HDi engine coupled with the additional range provided by the electric mode help it make short, economical work of long journeys. When the Peugeot 3008 HYbrid4 reaches a typical speed of over 120 kilometres per hour, the diesel engine takes over fully and the electric drive on the rear axle is disconnected from the powertrain.

The engineers at PSA carried out comprehensive calculations, simulations, and tests – with support from Bosch when it came to the electronic systems – to establish exactly when and how the two drives should work together and what kind of power they would have to provide to meet the driver's requirements as efficiently as possible. For example, the main requirement in the “Auto” driving mode – one of four settings – is to ensure minimum consumption with maximum driver convenience. The driver need only apply the gas and the electronic system automatically works in the background to control how the two drives work together. Naturally, the all-wheel drive can also be controlled manually and the driver can also choose between a number of other driving modes, ranging from very sporty to particularly economical.

Bosch ESP® developed specially for the Peugeot 3008 HYbrid4

ESP®has long played an important role in improving traffic safety. In critical situations, the electronic stability program intervenes in the operation of the engine and braking systems to ensure the vehicle remains under control. ESP® always incorporates the functions of the antilock braking system (ABS) and traction control (ASR).

To ensure that ESP® can also provide optimum support in the hybrid vehicles of PSA, both companies worked together to customise the functions specifically for the hybrid drive:

■The regenerative electric drive on the rear axle (RBC®) was restricted in order to safeguard vehicle stability in all scenarios.
■ASR settings were adjusted to match the selected driving mode in order to ensure the ideal balance between power and convenience for all road conditions.
■The electric vacuum pump was regulated – a second vacuum pump is required for the brake booster when in electric mode.
The high level of active safety exhibited by the Peugeot 3008 HYbrid4 is the result of close cooperation between PSA and Bosch.

Comprehensive Bosch drive package

In addition to providing systems know-how, Bosch was also involved in developing the primary components of the world’s first axle-split hybrid. One such part is the electric motor that is integrated into the rear axle. The tightly packed axle module left a space measuring 180 millimetres in diameter and 120 millimetres long to accommodate the water-cooled electric motor – known as the SMG 180/120 separator-motor-generator. From this cramped installation space, the permanent magnet synchronous motor generates a maximum output of 27 kilowatts and enormous torque of 200 Newton-metres. Its power rating is 20 kilowatts at speeds of up to 7,500 revolutions per minute.

In addition to the electric motor at the rear, the Peugeot 3008 HYbrid4 incorporates another Bosch permanent magnet synchronous motor. This SMG 138/80 (138 millimetres in diameter, 80 millimetres long) in the engine compartment acts as a high-voltage starter/alternator for the start-stop system. However, it is primarily responsible for supplying power to the rear-wheel drive (when the high-voltage battery is flat), electrical system, and air-conditioning system. The alternator is driven by the diesel engine via a robust belt. Since this alternator generates electricity in virtually all running scenarios while the vehicle is underway, the high-voltage battery, which functions as a buffer unit and energy storage device, can be configured as a cost-effective, compact unit. The power rating of the SMG 138/80 is seven kilowatts at up to 15,000 revolutions per minute. Its peak output is eight kilowatts.

The core element of the electric drive is the Hybrid Power Control Unit (HPCU). In addition to comprising the control software for both electric motors and the hybrid management, the power electronics also function as a pulse inverter that transfers the alternating current generated by the SMG 138/80 to the battery as direct current. Moreover, it acts as a direct-current converter between the vehicle’s low-voltage electronic system and the electric motor's high-voltage network. The demands on this component are incredibly tough, as it is expected to process currents of up to 340 amperes at a voltage of up to 300 volts in a space that measures only around 12 litres in volume.

Global market debut of the Bosch dual inverter

Bosch has never before produced a dual inverter that functions as a link between a high-voltage battery and two electric motors. However, engineers have now succeeded in realising this dual functionality in the same volume as the previous single inverter. “Conditions were already pretty cramped for our earlier inverters. The new dual inverters have taken that to a whole new level, though,” says Dr. Matthias Küsell, vice president of development and customer projects for hybrid and electric vehicles at Bosch, referring to the component’s complexity and high level of integration. Nonetheless, the engineers succeeded in ensuring the electrical components can be cooled properly and are not too close together, and were also able to develop lean production processes. Only the Bosch dual inverter can control both electric motors while the vehicle is running and manage the high currents that are generated at the same time.

All in all, Bosch ensured that four central components of the axle-split hybrid were ready for series production in the space of just two years. Although the engineers were able to draw on extensive experience accumulated over decades spent developing and producing electric motors, direct-current converters, and inverters, the tight timeframe and stringent demands set out by PSE still required a concerted effort. “In addition to hardware and software for the vehicle, we also developed test benches and testing software so that we could carry out accurate testing and measurements of the new products,” says Küsell.

The efforts paid off. As the first diesel hybrid and global debut of the axle-split concept, the Peugeot 3008 HYbrid4 is leading the way towards climate- and environment-friendly mobility. Its innovative drive concept shows that driving enjoyment, responsibility and economy can all go hand in hand – as can electric urban driving, thrilling offroading and convenient holiday travel with just a few refuelling stops.