|Protean in-wheel system. Click to enlarge.
Protean Holdings Corp, a developer of advanced in-wheel electric drive systems, has named Bob Purcell its Chairman and CEO. Purcell, best known for his leadership at the General Motors Corporation with the GM EV-1, moves into this role after serving as a board director and strategic advisor to the company.
Protean Electric designs, develops and manufactures the Protean Drive, a fully integrated, in-wheel motor, direct-drive solution. Each motor has a built-in inverter, control electronics and software, targeted at small- to full-size vehicles. Protean’s in-wheel motors are based on a modular redundant architecture, in which individual autonomous submotors are controlled by associated micro-inverters and work cooperatively to deliver the total power and torque or the motor as a whole.
Protean Electric has created a cost-effective, modular electric drive system designed for a wide range of vehicle applications. Protean Electric is moving aggressively from technology development and demonstration to volume production. My goal is for Protean to set the new industry standard for electric drive systems in partnership with industry-leading vehicle manufacturers and suppliers.—Bob Purcell
|Individual micro inverter/power electronics modules with embedded motor control software. Click to enlarge.
The distributed architecture offers system redundancy, as the failure of one sub-motor reduces performance but does not cause total system failure. Each sub-motor contains an embedded processor with control software that communicates with the System ECU (SECU). With the micro-inverters, heat is dissipated over a larger area rather than concentrated in a few very large semiconductors, the company says.
|The SECU. Click to enlarge.
Protean’s control system is a combination of an electronic control unit (ECU) and dedicated system control software, which together are referred to as the SECU. The SECU software is developed with model-based techniques using Simulink together with auto-code generation. The software can be supplied as individual Simulink modules, or as a complete control system for use on standard industry hardware such as dSpace MicroAutobox.
The SECU controls and manages motor and vehicle behavior based on a selection of system inputs. Each motor is directly connected to the SECU via a dedicated CAN bus.
The Brakes Controller function in the SECU is responsible for maximizing use of regenerative braking through interaction with an external brakes modulator, available from various manufacturers including Continental and Bosch.
When the driver applies the brakes, if the system is able to provide required braking using the motors, then the brakes controller will instruct the brakes modulator to hold-off the mechanical brakes so that maximum kinetic energy can be recovered. A failsafe system built into the brake modulator will ensure that friction brakes are applied if regenerative braking fails or if high brake pedal pressure is applied.
Protean is working on several aspects of “blending” regenerative braking and friction braking and integration with ABS systems. Protean says that it has an advantage over other electric vehicle drive systems in that in-wheel motors apply regenerative braking directly at each wheel independently, in a similar way to standard friction brakes.
Other solutions, such as the Toyota Prius, apply regenerative braking centrally, which involves transmitting braking torque through many mechanical components including differential and gears. Protean has developed a detailed Simulink model of blended braking in order to optimize the control strategy, ensuring maximal energy regeneration, dynamic stability, safety and seamless transitions between electric and hydraulic braking.
Protean is currently in production with the PD18, a motor designed to fit inside an 18 inch wheel rim. A range of other sizes are planned to support different types of passenger and commercial vehicles.
Purcell brings a long track record of electric drive experience to Protean Electric. From 1994 to 2002, he led the GM Advanced Technology Vehicles Group (GM ATV) that launched the GM EV-1. His group also developed and produced the S-10 Electric Truck and the GM Precept concept hybrid vehicle, part of President Clinton’s Partnership for a New Generation of Vehicles program. Many of the technologies that were pioneered at GM ATV are still widely used today throughout the industry in electric, hybrid and fuel cell vehicles. Purcell also served as Chairman of the GM-Ovonic advanced battery joint venture.
Prior to leaving General Motors in late 2008, Purcell was Vice President of Global Planning, Sales and Strategic Alliances at the General Motors Powertrain Group, where he was responsible for business and technology planning for GM’s global engine and transmission operations. His group also managed Powertrain’s $2 billion annual direct component sales and $1 billion technology licensing activities.