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 System ECU (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.
Standard driver controls, such as braking and acceleration demands, are supplied as electronic inputs to the SECU from appropriate sensors, processed in software, converted into torque and/or speed commands for each wheel, and communicated over CAN to the motors. The system is able to implement a variety of advanced vehicle control and dynamics features, such as ABS, traction control, and advanced stability control including torque vectoring. This is possible due to the ability of the motors to deliver independent positive or negative torque at each wheel in a fraction of a second.
To exploit this unique functionality, Protean has developed an open development platform that allows customers and researchers to develop and evaluate much more advanced vehicle dynamics algorithms than have been possible with existing propulsion systems. Protean’s SECU Simulink models are available to customers for integration into production ECU software or as a complete reference platform for prototype vehicle control and evaluation.
Some of the high-level functions provided by the SECU are listed in the following table.
Software Architecture
A top-level overview of Protean’s SECU Simulink model is shown in the architectural diagram below.
The arrows indicate the flow of information, and the building blocks identify logical software boundaries that include vehicle control functions (green) and safety functions (red). The system is fully designed to incorporate parallel monitoring systems as used widely within the industry.
Six core modules make up the system
1. Vehicle and System State Controller
The vehicle and system state controller is the core software function that interconnects and controls each device’s inputs and outputs to the vehicle. It coordinates operations and monitors the entire system to ensure fail-safe operation. It undertakes continuous diagnostics and reporting functions to the driver-user interface.
2. Brakes Controller
A key function of “in-wheel” motors is to conserve energy through regeneration during braking. The brake controller resolves friction and regeneration braking based on driver demand and system capabilities, e.g. battery charge limits and status.
3. Motor Controller
Each “in-wheel” motor is controlled independently from the ECU to ensure coordinated operation. The software monitors each motor and handles failure conditions in a safe way.
4. Energy Controller
Effective battery management is critical to the performance and reliability of hybrid and electric cars. This software module communicates with the battery management systems and controls system operation based on energy storage status and capabilities.
5. Accelerator Controller
The accelerator is integral to the system controls. It links through the System State Controller to the other controller modules to ensure that the “in-wheel” power is matched to the vehicle’s performance ability.
6. Chassis Dynamics
Matching delivered torque to the capability of each tire is critical to ensuring good drivability within the full EV solution. A software model of the vehicle’s dynamics is modeled in the ECU and used by the dynamics control algorithms and associated functions to improve vehicle handling – this would include traction controls and ABS.
Protean chose to package the inverters on the in-wheel motor itself, eliminating the multiple cabling and performance challenges caused by packaging the inverter on the vehicle body. This reduces cabling requirements drastically and frees up yet another package volume on the sprung mass, further increasing the packaging flexibility on the body offered by the in-wheel motor concept.
Protean’s in-wheel motors are designed for high reliability and are based on a modular redundant architecture. Individual autonomous sub-motors are controlled by associated micro-inverters and work cooperatively to deliver the total power and torque for the motor as a whole.
Key features include:
- Very high torque and power density
- Very high braking torque across a wide speed range
- Unique modular architecture based on sub-motors
- Design for mass production
- Ability to enable miniaturization and mass production of power electronics as part of motor assembly
- No need for large separate power electronics unit
- Redundancy and fault tolerance
- Unique technology covered by multiple patent applications