Protean Electric courts partners for wheel motor applications
24-Jun-2010 20:09 GMT

Compact design is evident in this cutaway of Protean Electric’s electric wheel motor. Note thin power-electronics modules (marked with green/grey circles) arrayed around the outside surface of the rotor.

More than a century after Ferdinand Porsche used them on his first car, and after decades of their use in giant off-road vehicles, are electric wheel motors finally ready for light-duty applications? A small U.K.-based engineering company with some unique technology and plenty of dedication is betting they are.

Protean Electric has been developing electric motor technologies since the 1960s and built its first wheel motor for automotive use in 2003. In recent years the company has fitted the innovative pancake-shaped motors to various concepts and prototypes, including a Volvo C30-based series hybrid, a Ford F-150 EV with an individual motor at each wheel, and a Mini EV, among others.

The company is seeking customers who would license its design for production, and CEO Craig Knight believes the U.S. market is the ideal place to find them.

“We’re appealing to the U.S.’s love of larger vehicles—SUVs, minivans, pickups—for which we think wheel motors are the perfect fit for vehicle electrification to improve efficiency,” said Knight. “With four wheel motors, we can deliver more torque directly to the drive wheels.”

He said that by employing the Protean motors, an OEM or Tier 1 can create a simpler, lower cost drivetrain and improve vehicle control and overall efficiencies by eliminating the losses typical in mechanical power transfer. Also, it can increase output by increasing wheel diameter.

He said wheel motors are more than 90% efficient in terms of converting energy into vehicle propulsion, enabled in large part by their capability to regenerate most of the vehicle’s braking energy under deceleration.

Better wheel control, grip

The simplest wheel motors integrate an e-motor into the wheel hub, creating a stator-rotor arrangement to generate torque when power is applied to the stationary coils. More sophisticated designs (including Protean’s) are liquid-cooled, and some even include suspension components. Michelin’s Active Wheel, Siemens’ eCorner, and developments from Canada’s M4 Technologies and General Motors are recent examples of interest in the technology.

In 2003, AEI drove a prototype hybrid-electric Chevrolet S-10 equipped with two 25 kW (33 hp) wheel motors sourced from Italy-based motor specialist Lucchi R. Elettromeccanica. The motors fit neatly within the truck’s 18-in-diameter (457-mm) road wheels. The rear-drive system was engineered by GM and partner Quantum Technologies with dedicated power control and coolant solutions.

In the S-10, the wheel motors provided nearly 60% more torque to the drive wheels than was available from the truck’s combustion engine and gave it prodigious acceleration, traction, and grip—wheelspin was eliminated—when tested on a drag strip and slalom course. Reporters who sampled the e-drive S-10 were impressed by its performance. Development did not proceed, however, nixing the logical next step: electric all-wheel drive.

Knight noted similar potential benefits of Protean Electric’s wheel motors, plus the capability to precisely control the amount of torque to each wheel, aiding traction in varying road-surface conditions and providing greater maneuverability.

Submotor architecture is key IP

Protean’s three-phase permanent-magnet motors are scaled for vehicle curb weights of 5000-6000 lb (2268-2722 kg). They are rated at 84 kW (113 hp) peak power for 20 s, and 54 kW (72 hp) continuous, depending on battery power.

According to Knight, the company’s key intellectual property is in the submotor architecture and its integration with the microinverter technology. Each motor features distributed architecture, incorporating one inverter and eight power-electronics modules within the motor, rather than residing in a separate unit. Each module handles one-eighth of the input power.

The wheel motors are designed to operate using open-source control software and integrated with the vehicle via CAN. Profiles of the copper-wire windings are proprietary, and Protean has developed a robotic winding process. “The entire unit is designed for manufacturability,” Knight noted.

The motor’s stator and power electronics are liquid-cooled. Knight noted that the company’s 72 engineers (out of a total staff of 86) have put much of their development focus on increasing cooling efficiency.

The design integrates the brake rotor on the back side of the electric motor’s cast-aluminum rotor. It fits an 18-in wheel and is intended to use the OEM’s existing bearing set.

A disadvantage of wheel hub motors that has yet to be fully solved is added unsprung weight, which negatively affects the vehicle’s handling and steering. GM’s wheel hub motors added 33 lb (15 kg) to each 18-in wheel, which GM engineers said could be offset by tweaking suspension damping and spring rates. Knight acknowledges that unsprung weight is a potential issue that is being addressed through design.

The integration of electric drive motors and various vehicle components into a vehicle’s wheels has the potential to enable fresh, unique new vehicle designs by freeing up the space traditionally occupied by the powertrain and related accessories. They are also one of the major components of a true “by wire” electrified propulsion system.

The F-150 fitted with Protean’s wheel motors has racked up thousands of test miles and recently received upgrades, including an integrated braking system, at the company’s Romulus, MI, facility. Knight said he welcomes OEMs or suppliers to collaborate with Protean on an SUV or minivan to demonstrate the technology’s performance potential.

Lindsay Brooke

Powertrains – Automotive Engineering International Online

AZD’s next-gen hybrid and EV systems will bring innovations, lower cost
24-Jun-2010 20:45 GMT

AZD’s new technologies being prepared for 2012-13 will leverage learnings gained from developing the electric drivetrain for Ford’s 2011 Transit Connect EV (shown). The vehicle will arrive in the U.S. as a glider from Ford’s Turkey assembly plant, and AZD will upfit the electric driveline in an ex-AM General facility in Livonia, MI.

When they enter production in the 2012-2013 timeframe, Azure Dynamics’ next-generation hybrid and electric propulsion systems will feature new approaches to battery cooling, power control, e-motor design, and systems engineering. The changes are aimed at further reducing the bill of materials and overall cost of the electrified powertrain, as well as improving performance.

“All the programs we’re doing this year basically are engineering programs in which we’re engineering cost out of the system,” said company CEO Scott Harrison. “We’re taking 40% cost out of our Balance hybrid system, but we’re also working on future component and systems designs that will provide greater customer benefits as well as lower cost.”

Azure Dynamics (AZD) currently upfits the Balance hybrid architecture on Ford’s F-450 chassis for a growing list of Class 3-5 commercial fleets including FedEx, Purolator Courier, and AT&T. AZD also is supplying its Force Drive battery-electric drivetrain for Ford’s 2011 Transit Connect EV.

The Force Drive is claimed to provide 80 miles (129 km) electric range per full charge. It features a Siemens drive motor and a new lithium-ion battery pack supplied by JCI-Saft, which in early June took a 3.4% equity stake in AZD. AZD is handling the program’s vehicle integration. Beginning this fall, it will install the electric drivetrain into Transit Connect gliders at a leased AM General facility in Livonia, MI.

New motors and controllers

In an interview with AEI at AZD’s U.S. headquarters near Detroit, Engineering Director Jim Mancuso outlined technical opportunities to improve system efficiency and reduce cost.

“We’re probably in Generation 2 in terms of our current technologies; Gen 3 is about two to 2.5 years away,” he said. “We’re moving to common parts and systems across platforms. Every vehicle we build uses a vehicle control unit (VCU) that is common to an ECM on gasoline-engined vehicles. The technology comes from a partnership we formed with the supplier back in 2004, and the volume has risen to the point where we now see some cost reduction.”

He noted the light-duty Force Drive system uses the same controller hardware as used in AZD’s medium-duty Balance hybrid. Also common among the two platforms are the DC-DC inverters, which are calibrated and wired differently for the vehicle application.

The Siemens motor on the Transit Connect EV is the identical electric machine AZD previously used on a series-type hybrid product.

“It’s all about working with our suppliers to ensure the individual components we’re developing are not going to be used only for an individual product; they’re going to be used across the board on multiple products,” Mancuso said.

“In the case of this particular motor we invested a lot of time in understanding its capabilities within our system. Using it reduces our risk immensely—and reduces the time for our engineering team to integrate it. I’d say we’re pretty good at standardizing hardware,” he asserted.

The Transit Connect EV is AZD’s first series production foray into light-duty systems. Harrison said that while the company’s focus remains on the medium-duty segment, all future product is being developed to cover a broad span of vehicle sizes and applications, in order to build scale.

“That goes for controllers and electric motors,” Mancuso explained. “The next-gen controller will feature newer IGBT (insulated-gate bipolar transistor) technology. It will be physically smaller. In motors, there’s a general trend toward permanent-magnet AC machines and we’ll be there, too.”

The company’s design engineers based in Vancouver and software designers based near Boston are working closely on motor development because the machine’s characteristics impact so much on the control side. Mancuso said AZD is “looking at some new ways to control DC-DC inverters via CAN.”

A clutched FEAD and fast charging

AZD’s incumbent battery pack is liquid-cooled, and company engineers have debated the superiority of both types. Currently they are investigating air cooling because some key suppliers are working on new approaches to air-cooled packs that are expected to be ready “in the next three to four years,” Mancuso said.

He indicated the new air-cooled designs would be integrated with the vehicle’s climate-control system or perhaps use cooling fans.

AZD’s switch to lithium-ion battery cells from the nickel-metal hydride currently used will bring a significant portion of the 40% systems-cost reduction they expect to achieve in the next year, Harrison concedes. But another new feature that Mancuso claims is an “industry first” has him excited about its potential to impact cross-vehicle efficiencies.

The new version of the Balance product adds a clutched front-end accessory drive (FEAD) system, which enables the belt-driven power steering pump, A/C compressor, etc., to be coupled and decoupled alternatively from the electric motor and combustion engine, depending on the vehicle’s drive mode.

“There was a lot of mechanical engineering that went into this system to make it robust; we erred on the ‘high side’ of robustness,” Mancuso explained. “The clutch is a heavy-duty design that we developed with a supplier.”

Without providing specifics, he said adopting the clutched FEAD opens the door for various cost reduction opportunities elsewhere in the vehicle.

Higher system voltage and fast charging are other technology areas Mancuso said AZD is investigating for the next-gen powertrains. He recalled his learnings from an early AZD vehicle built for Purolator that featured a 600-V system.

“I was responsible for that program, and I still can’t believe how the performance increased when we added a ‘boost leg’—an inverter and motor control that raised our voltage from 300 V to 600 V but added very little hardware,” he said. “We’re doing a lot of research on a similar arrangement but not yet committed to it.”

The issue of fast charging in EVs and plug-in hybrids is getting a lot of attention in the industry, but AZD’s customers aren’t yet requesting it, Mancuso noted. “They tell me it’s not yet a necessity for them, but I think two to three years down the road our next generation’s products will have to have that capability. Our battery supplier will have to design around that, and they’re talking about 480 V.”

Lindsay Brooke

Powertrains – Automotive Engineering International Online

New simplified hybrid drive systems from Hyundai, VW, and FEV reduce cost

10-May-2010 21:27 GMT

Hyundai clutch (left) nests in the electric motor and connects to the engine flywheel. When the clutch is engaged, the engine and motor are locked for engine-only or acceleration assist (hybrid) operation. When the clutch is disengaged, the e-motor alone drives the vehicle through the six-speed automatic.

Automakers recognize the need for hybrid-electric powertrains to help meet tightening fuel economy standards, but costs of the full-feature designs currently in production are leading two OEMs to produce less expensive configurations.

Starting later this year, Hyundai and Volkswagen will introduce parallel-hybrid configurations that provide all-electric drive, electric assist, regenerative braking, and idle stop/start. They’ll connect to production automatic transmissions rather than purpose-built transmissions with two integrated motors. Hyundai begins with the front-drive Sonata hybrid; the Kia Optima follows. VW starts with rear-drive Touareg and Porsche Cayenne hybrids.

Also emerging for industry consideration is a prototype by FEV shown at the 2010 SAE World Congress. In FEV’s design, one motor provides all hybrid functions, including A/C compressor operation, in a seven-speed AMT (automated manual transmission).

The acceleration/load electric-assist system with its smaller battery pack is a low-cost design proven by Honda, which calls its system the Integrated Motor Assist or IMA. But the inability to provide all-electric operation limits its effectiveness. And although a two-mode hybrid as developed by Allison, GM, and other makers offers the additionally sought improvement in highway fuel economy, along with the ability to haul payloads and tow, its widespread application is limited by cost.

The Hyundai and VW designs both feature a computer-controlled hybrid clutch between engine and motor—a wet multidisc clutch and 30 kW motor for Hyundai, and a single dry clutch and 38 kW motor for VW.

When the hybrid clutch is disengaged, the motor alone drives through the transmission to power the car in all-electric mode, and both systems launch that way from a stop. When the clutch is engaged and the engine is running, power then flows from engine through motor to transmission. The motor just spins as if part of the flywheel in the Hyundai system; on the VW system, the motor functions as a generator if needed.

If there is the demand, battery current is supplied to the motor for acceleration/load assist. On deceleration, the motor also may operate as a generator for regenerative braking.

Hyundai: 62 mph in EV mode

Hyundai adds a belt-driven high-voltage motor/generator (8 kW) to the 2.4-L four-cylinder, in place of a conventional generator. It provides engine start and charges the 270-volt hybrid battery pack by allowing the engine to run even while the vehicle is moving in all-electric mode.

Compared with the 33 kW and higher generator/motors integrated into other systems, this design appears to be considerably less expensive. However, to enable all hybrid functions with just one motor would require an additional clutch, as in the torque converter of the VW system. Hyundai eliminated the torque converter for packaging and improved efficiency.

Hyundai employs a computer strategy that controls fuel injection for the engine and electric-current feed to the motor to synchronize rpm, for smooth hybrid clutch engagement during the rolling launch, explained Woong-chul Yang, President of the R&D Division of Hyundai-Kia.

A 270-volt pack with lithium-polymer cells is used. Hyundai claims it is the first U.S.-market application for Li-polymer in a non-plug-in hybrid vehicle. It is reportedly intended to give the maker field experience with this type. Combined with the belt-drive generator/starter, the pack apparently enables more all-electric operation while an optimized charging schedule is maintained.

Conventional hybrids typically increase only city fuel economy compared with non-hybrid versions, with the two-mode system being the price-premium exception. However, Hyundai uses the 30 kW motor to drive the car through the six-speed automatic at speeds up to 62 mph (100 km/h). This helps boost hybrid highway fuel economy from the 35 mpg of the conventional Sonata to a claimed 39 mpg.

Hybrid clutch is key to VW’s system

VW made only modest modifications (primarily an electric oil pump and new torque converter) to the eight-speed automatic used in the conventional Touareg. The entire hybrid module fits into the space between engine and transmission without modifying the vehicles. A 288-volt Ni-MH battery pack is used.

Although the VW design allows all-electric operation at up to 36 mph (60 km/h), the Touareg/Cayenne still must satisfy customers expecting V8 levels of torque. So the 3.0-L V6 is supercharged, rated at 329 hp and 326 lb·ft (245 kW and 440 N·m, respectively), with a tow capacity of 7700 lb (3493 kg).

The tow requirement dictated use of a torque converter, so VW took advantage of its lockup clutch to permit the single motor/generator to also perform the start function.

From a stop, the vehicle launches in electric drive with the motor/generator—hybrid clutch disengaged and the torque converter lockup clutch closed. The lockup clutch then is control-slipped, the hybrid clutch is engaged, and the motor cranks the engine.

At suffciently high rpm, fuel is injected and the engine starts. The hybrid clutch is released so the engine can rev without load to a computer-requested setpoint to match the speed of the motor/generator, at which the hybrid clutch (and lockup clutch) then can be engaged. It’s all instantaneously smooth, according to VW engineers.

When the driver lifts his foot off the accelerator at cruising speed, the computer stops the engine and de-energizes the motor, and the vehicle coasts freely to boost highway mileage, noted Dr. Bernd Stiebels, VW hybrid powertrains manager. Fuel economy numbers have not yet been announced.

Because the engine is supercharged, VW’s hybrid requires a more complex cooling system. Motor electronics and charge-air cooler are in one circuit with an electric pump and two small radiators.

The engine and transmission, electric motor, and passenger compartment heater are in another circuit with a large radiator. This circuit includes an electric pump and, to speed warm-up, a vacuum-controlled blocking cover for the engine mechanical water pump, to inhibit coolant circulation through the crankcase.

FEV’s 7H-AMT concept

Conventional AMTs typically have been limited to vehicles where smooth shifting isn’t a priority. But FEV’s one-motor 7H-AMT provides fill-in torque when the electro-hydraulic shifters make gear changes, which eliminates the lurching effect typical in AMTs. Four gears are direct; three are overall ratios from gear pairs.

The FEV prototype has a single dry clutch between the engine and transmission; its electric motor is located on the transmission. With the clutch engaged, the vehicle can operate entirely with the engine or in electric assist; or with the clutch disengaged, it operates in all-electric mode.

The transmission is a three-shaft design, with a 35 kW electric motor on one shaft, simplifying use of the motor to torque-manage shifts. Further, if the vehicle is running entirely on the gasoline engine and the battery pack needs recharging, the motor of course just operates as a generator.

The engine is started by controlled slip of the clutch and computer modulation of motor torque. As the vehicle launches entirely on electric power, the engine will start with the transmission engaged as high as fifth gear. The 7H-AMT permits all-electric operation at speeds as high as 42 mph (70 km/h).

The idle-stop A/C compressor operation is a cost-saving bonus. The 7H-AMT has a belt-driven conventional compressor with a magnetic clutch, which can be engaged to operate with engine power or hybrid motor power. This eliminates the need for the comparatively expensive electric motor-drive compressor.

Paul Weissler

Volkswagen Touareg and Porsche Cayenne Parallel full hybrid technology from Bosch goes into series production · Launch of first full hybrid vehicles with parallel technology · Intelligent drive control system provides key to extraordinary comfort · Bosch-made power electronics, electric motor, and adaptive clutch The hybrid variants of the Volkswagen Touareg and Porsche Cayenne S, which recently went into production, feature hybrid technology supplied by Bosch. This is the first time that either of these models has been available as a parallel full hybrid. As well as key components such as the power electronics and electric motor, Bosch is also providing the “brain” of the vehicles in the form of the Motronic control unit for hybrid vehicles, which governs when the electric motor, internal-combustion engine, or a combination of the two kick into action. Volkswagen and Porsche both chose to equip their hybrid vehicles with a 3.0-liter V6 supercharged direct-injection engine and an eight-speed automatic transmission. The six-cylinder V-engine delivers 245 kilowatts (333 horsepower) and a maximum torque of 440 Newton meters starting from 3,000 rpm. The vehicle also features an Integrated Motor Generator (IMG) developed by Bosch. The water-cooled electric motor includes a separate clutch.

The hybrid module is positioned between the internal-combustion engine and the transmission, taking up impressively little space thanks to a diameter of 30 centimeters and a length of just 145 millimeters. The IMG delivers 34 kilowatts and a maximum torque of 300 Newton meters. That means the Volkswagen and the Porsche can cruise at a maximum of 50 to 60 kilometers per hour running on electric power alone, as long as the nickel metal hydride (NiMH) battery has enough charge. The battery has an energy capacity of 1.7 kilowatt-hours with a peak of 288 volts. During braking, the electric motor – now operating as a generator – recovers kinetic energy, which is then stored in the high-voltage battery. Lifting off the throttle at any speed up to around 160 kilometers per hour activates what the engineers refer to as ‘sailing’ mode: the combustion engine automatically shuts down and the vehicle coasts along without consuming fuel – obviously without sacrificing any of the functionality of the systems required for a safe and comfortable drive. Braking is also a fully automatic process, with the hybrid control unit monitoring the pressure on the brake pedal to determine what brake torque should be electrically set by the IMG. This does not affect safety systems such as ABS and ESP®, which take precedence whatever the situation. ‘Power boost’ from the electric motor For drivers in a hurry, the electric motor and the combustion engine can also work in tandem, allowing the Volkswagen and the Porsche to sprint from 0 to 100 kilometers per hour in 6.5 seconds. This ‘power boost’ function increases the vehicle’s performance to 279 kilowatts (380 horsepower), offering the driver a maximum torque of 580 Newton meters. Compared to the first-generation V8 vehicles, these hybrid vehicles cut fuel consumption by up to 40 percent. EU cycle fuel consumption falls to 8.2 liters per 100 kilometers, equivalent to CO2 emissions of 193 grams per kilometer. Both vehicles also comply with the Euro 5 standard and the U.S. emissions standard ULEV 2.

Intelligent control system provides key to extraordinary comfort The fact that the internal combustion engine and the electric motor work together so seamlessly stems from the perfectly tuned interaction between modern management and control technology and optimized hybrid components. Bosch can draw on many years of experience in this field thanks to its work on developing gasoline injection systems. “The hybrid control unit injects a healthy dose of innovation into the best field-proven technology. We based the system on the Motronic, which has already proved its worth in so many direct injection gasoline vehicles. We then integrated the additional functions you need for hybrid operation, which we developed in collaboration with our customers,” says Matthias Küsell, who heads up development and customer projects for hybrid and electric vehicles at Bosch. One of the biggest challenges was ensuring a smooth transition between electric-powered, hybrid, and combustion engine-powered driving. It was essential to ensure that driving comfort would not be impaired by the switch between drive and generator operation. This is achieved by giving the control unit continuous access to sensor data from the combustion engine, electric motor, battery, clutch, and other components. It uses this data to analyze and control how the two powertrains interact in real time, using an adaptive clutch to make seamless transitions.

The control unit ensures that the electric motor and engine are turning at exactly the same speed when transferring the torque. Küsell sees this as the core element of the parallel hybrid technology. Hybrid and direct injection engines – the perfect combination The supercharged V6 engine is a key part of the overall concept. The Motronic control unit manages the combustion engine with tremendous precision, right down to the rate of individual injections. It employs an additional CAN bus interface to exchange all relevant data with the hybrid components, power electronics, and battery, and the efficient direct injection system also reduces exhaust emissions. The combustion engine and electric motor complement each other perfectly, enabling parallel hybrids to offer a whole series of new features to improve driving comfort. Active Damp Control is the name Bosch chose for the concept that provides the six-cylinder engine with the sedan-like feel of a much larger engine. In the future, this concept is set to iron out some typical disadvantages of smaller turbocharged engines such as poor low-end torque, paving the way for highly economical downsizing concepts to enter the mass market. Optimized components offer inroads into mass market Parallel full hybrid technology can be implemented as a more cost-effective solution in comparison to other hybrid concepts. For example, it requires just one electric motor, which operates as both a motor and a generator. To enable broader application of this environmentally friendly technology in different classes of vehicle, Bosch is engaged in a continuous process of developing the system on a component level, tackling issues such as reducing the volume of space taken up by the power electronics. Despite having to maintain a tricky balance between robust design, maximum efficiency, and minimal space requirements, the developers have now succeeded in reducing the volume of the power electronics by one third to ten liters – without compromising performance. “Our aim is to get the next-generation version down to five liters,” Küsell says. The power electronics are a core component, providing an interface between the high-voltage electric drive and the vehicle’s 12-volt electrical system, and featuring an inverter that converts the direct current from the battery into three-phase alternating current for the electric motor, and vice versa.