ISE has developed a proprietary system control architecture for use with the ThunderVolt® drive system. The hybrid and drive control software is an integral part of the system. The vehicle interface is provided by the vehicle controller, which is based on a high speed automotive J1939 multiplexing system manufactured by STW in Germany. It also provides an interface to displays and standard vehicle electronics such as GPS. The CAN bus architecture of the ThunderVolt® vehicle control system has been greatly simplified over the last three years. All major vehicle subsystems (Motive Drive, APU, Energy Storage, Vehicle Control, and Accessories) communicate on one single CAN network. This simplifies and improves vehicle data acquisition and maintenance. All major vehicle subsystems can be accessed via one data port. Custom programming is performed jointly by ISE and Siemens. The computerized control network on the bus relies on distribution boxes to monitor, fuse, supply, and/or switch power to high power components.

Over the past five years, ISE has invested considerable effort into perfecting what we believe to be the most sophisticated series hybrid energy control system in the world. In close collaboration with Siemens, we have focused recent efforts on closed-loop generator control and a new rapid engine start/stop technology enable by this procedure.

Closed-loop generator control enables us to operate a combustion engine at virtually any speed while supplying a constant bus voltage. This increases the efficiency of the drive system because we can operate the engine at maximum load. Competing hybrid systems must change engine speed to adjust their intermediate bus voltage, which becomes increasingly inefficient under partial or no load. Furthermore, the closed-loop feedback enables the ISE hybrid system to automatically stop the engine whenever its operation is unnecessary, such as during stops when the engine would otherwise be idling. The engine is then restarted with the generator, increasing starter life. This can be achieved without injecting fuel, which cools the engine down rapidly to reduce heating. This process facilitates operation in the "all-electric" mode, when the vehicle operates solely on battery power.

Distribution  Platform Allows easy addition of options Centralizes diagnostics/control signals Contains all fuses and breakers

Vehicle Subsystem Controller (Nodes) Vehicle rated computer - dual CAN ports Manufactured by STW Software by ISE

Conversely, another advantage of the ISE closed-loop process is the capability of operating in a "diesel-electric" mode, where the generator energy is directly transferred to the drive motors, bypassing the batteries. This operating mode improves battery life by reducing the number of battery charge/discharge cycles. It also enables the ISE hybrid system to function in the event the batteries become unusable for any reason, providing added redundancy. With the 160 kW Siemens generator, degradation of vehicle performance in the event of a battery failure is modest.

The ISE control system also offers vehicle users a high degree of operational flexibility. The amount of battery energy used can be adjusted to the type of operation by changing hybrid control parameters - a process so simple it can be performed "on the fly." For example, the system can be optimized to achieve absolute maximum fuel economy by maximizing dependence on the battery packs, or adjusted to maximize battery life by using the battery energy more sparingly when fuel is cheap or more readily available. Given the high cost of battery replacements, this type of flexibility can greatly reduce life-cycle costs. When new components are added to the ISE hybrid drive system, control system changes are usually limited to reprogramming of the "node," or microprocessor, responsible for controlling that subsystem.

As an integral part of the Vehicle Control and Diagnostics subsystem, ISE offers the unique capabilities of our Remote Diagnostics Unit (RDU), which allows monitoring of the entire drive system and all of its components from remote locations. This is achieved by transmitting diagnostic information via a wireless link. The RDU complements other ISE diagnostic systems that supply basic data on vehicle status to operators via dashboard displays, and that allow trained maintenance personnel to access additional data by plugging laptop computers into the vehicle data network. To implement the RDU concept, each vehicle has its own cellular number or Internet address. When the on-board health monitoring system detects a problem, the vehicle automatically e-mails either the fleet operator or the manufacturer with a summary of the relevant information. This could include time, vehicle location, driver's identity, error messages, and any amount of supporting data. In addition to e-mail feedback, an external user is able to "dial into" the vehicle and request a subset of real-time data. Vehicle speed, temperatures, and voltages can all be read to determine the severity of the problem. With proper authorization, the external user can control certain aspects of the vehicle to help diagnose the vehicle's problem. This capability can easily be expanded to include the reporting of such information as fuel usage, average speed, passenger or cargo loading, battery health, periodic maintenance, duty cycle, and anti-theft functions. The RDU also enables ISE engineers in San Diego to assist customers in troubleshooting the drive systems in the their vehicles.