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Holden’s EFIJY Show Car Powered by V8, controlled by PICAXE The Holden EFIJY show car was one of the most popular vehicles on display at the 2005 Sydney International Motor Show. While the stunning looks and technology drew the crowds, few people would have been aware that the majority of the electrical systems in the vehicle were controlled by PICAXE microprocessors. By JEFF BROWN* 8  Silicon Chip siliconchip.com.au H OLDEN INNOVATION IS Holden’s research and development centre and one of its functions is to develop and demonstrate new technologies and concepts. Vehicle design is moving more and more into the virtual world but technology still needs to be demonstrated to allow people to decide if they want this in a future vehicle. Invariably, this requires a demonstration or concept vehicle. The concept vehicle may be based on a current production car and have the new technology integrated into it or in the case of EFIJY, it became a completely new vehicle. With the increasing complexity of today’s vehicle electrical systems and the integration of mechanical and electronic control systems, it can be quite difficult to adapt or modify the base vehicle to accept the new technology, even with the benefit of having detailed information about the vehicle’s architecture. Traditionally, first-tier suppliers provide the components and in some cases the technology used in a given subsystem. Typical development of a component for production involves a number of charges from the supplier; including design and development charges, tooling charges and, of course, piece cost. When a prototype is produced, the supplier incurs many of the same costs. It costs almost the same to write software for a one-off prototype as a production system. In the case of the production system, the software may be more complex to increase the robustness of the code but most of the requirements will be the same. A similar issue occurs with hardware. In the case of PC boards, design work still needs to be done, again perhaps not to the same extent as production, but still a significant percentage of the work. This all leads to significant expense to produce a single working prototype. A simple change to add a customer feature may result in charges of $5$10,000. A more complex system can see the cost escalate to $250,000 to demonstrate a new technology. Therefore, significant budgets are required. By developing a low-cost prototyping system in-house, Holden is able to investigate and demonstrate new systems at much lower costs and ensure any intellectual property remains with Holden. Why PICAXE? LCD panels are used for the large instrument panel screen and for the central touch-screen display. siliconchip.com.au Many of the engineers at Holden are readers of SILICON CHIP magazine and recent articles about the PICAXE range of microcontrollers sparked some interest due to our previous experience with the Microchip range. The need arose for a relatively simple project and the PICAXE looked like it might be suitable, while giving us the opportunity to evaluate the product. Our initial selection was the 18X processor and in the target application, it proved to be very competent; the simple interface and relatively January 2006  9 screens are LCD panels, each controlled by compact PCs with embedded Windows XP operating systems. The on-screen images for the touch screens were created by Holden’s Design Department specifically for EFIJY and are running in Macromedia Flash. The touch screens interface with Flash and communicate with the outside world via the PC’s serial port. This results in each “button press” on the touch screen being transferred to the subsystem the driver intends to control. A dedicated module based on an Atmel Mega16 programmed in BASCOM handles all serial traffic with the PCs and sends and receives commands from the modules that control most subsystems. A second Atmel micro handles communications with the engine and transmission CAN (Controller Area Network) networks for data such as RPM and vehicle speed for display on the instrument panel and also controls the ignition and start systems. CM4 control module Developed especially for the EFIJY, the CM4 is a general-purpose control module for use in a variety of applications. It uses a PICAXE 40X running at 16MHz and includes a high-current H-Bridge for controlling motors, high-current FET outputs for switching lights, solenoids etc, analog inputs, and digital inputs with jumper selectable pull-ups or pull-downs. simple BASIC language resulted in very fast prototyping of a concept. Holden Innovation has now used the PICAXE 08, 08M, 18A, 18X and the 40X in numerous applications. Over time the complexity of the projects in which we have utilised the PICAXE for has increased and we now base most projects on the 40X running at 16MHz. The most interesting aspect of the PICAXE is the number of users, some of whom do not have an electrical background. We have found that the simple interface and language has been readily adopted by students 10  Silicon Chip and engineers, and even by hardcore programmers. EFIJY electronics With the exception of the engine and transmission control modules, the electronic systems in the EFIJY are unique and are not based on production components. They use a total of 11 microcontrollers: nine PICAXEs and two Atmel AVRs. The most visible systems when sitting in the vehicle are the large instrument panel screen and the central display, revealed when the centre compartment opens. The two touch Holden Innovation developed the CM4 module as a general purpose control module that could be used for a variety of demonstrator applications. It’s called CM4 because it is the fourth in a family of control modules developed by Holden Innovation. The heart of the CM4 is a PICAXE 40X running at 16MHz. This module has a high-current H-bridge with current measurement for controlling motors, high-current FET outputs for switching lights and solenoids, etc, plus analog inputs and digital inputs with jumper-selectable pull-ups or pull-downs. In addition, a resistor network is employed for resistor-encoded switching to further increase the number of available inputs. This is achieved using one of the 40X’s analog inputs and a resistor ladder; by switching points on the ladder to ground, 10 steps at 0.5V per step is achieved. Therefore, the 40X can process 10 different inputs on the one analog input. The power supply is capable of providing 5V for various sensors and the PICAXE has the ability to control and switch its own power supply off for any house-keeping required before a controlled system shutdown. This is very handy for functions that need to be controlled after the ignition has siliconchip.com.au been turned off. The usual PICAXE features such as serial communications, I2C, etc, are also available. PC board design and fabrication of the CM4 was conducted in-house by Holden’s Instrumentation department. EFIJY uses four CM4 modules for the following subsystems. ePark Brake EFIJY is fitted with an electric park brake which offers a number of features, including removing the need for a large and bulky lever. The pushbutton is pressed to apply and pressed to release the parking brake. In the event the parking brake is required as an emergency brake, the rate of brake application limits the vehicle deceleration to 0.3G. Operation of the system is via an actuator operating on a conventional park brake system located within the rear wheels. This actuator is controlled via the H-bridge and uses both positional feedback and current through the H-bridge. This allows the system to be self-adjusting and provides the control algorithm with a measure of load applied. Entry and exit Entry and exit from the vehicle is interesting, since there are no door handles in or outside the vehicle. Pushbutton switches for the doors and boot use the resistor encoded inputs to the CM4 module to control release solenoids. There is also a custom remote control based on a surface-mount version The driver selects the gear by pushing one of the buttons located on the centre console. These buttons use the resistive encoded inputs on one of the CM4 modules, while the actuator (which controls the transmission) is controlled via the H-bridge output. of the PICAXE 08M. This operates on 433MHz and has three pushbuttons that release the doors and boot in a conventional manner. The vehicle responds to the command from the remote and starts a power-up sequence to ensure all systems are ready for operation when the driver enters the vehicle. The third method of entry is via a passive entry system. The operator walks up to the car, holds out his/her hand and the door pops open to meet it. In this mode, the vehicle detects the presence of a valid remote. This is achieved using a multi-axis motion sensor controlling the power supply in the remote. This allows the remote to power up for brief periods. A unique message is then transmitted but only if the remote is moving. This significantly increases battery life – if the remote is in storage or not in use, the power supply to the 08M is off. When this message is received by the CM4, the door proximity sensors are enabled. These use a capacitance type proximity sensor based on the The central display is revealed when the centre compartment opens. It displays touch-screen images (controlled by compact PCs) to control functions such as the radio and the suspension settings. siliconchip.com.au January 2006  11 The headlamps use 20 high-brightness LEDs in the centre, while the outer rings use 36 pairs of white and amber devices (the latter for turn indication). A 6-litre LS2 V8 fitted with a supercharger sits in the engine bay. It develops 480kW of power and 775Nm of torque. velops 480kW of power and 775Nm of torque. You start the engine with the large pushbutton on the left of the instrument cluster. Starting is controlled by one of the Atmel Mega16 microcontrollers, which provides interface to the power control and engine management systems of the vehicle. When a valid remote transmitter is detected within the passenger compartment, the start button flashes to indicate that the engine can be started. Pushing the button for a brief period then starts the engine. To stop the engine, the start button is pushed again. Various interlocks ensure that the engine is not cranked if it is already running. Alternatively, a key can be used to turn on the ignition and the start button used to crank the engine. ePRNDL When a valid remote transmitter is detected inside the passenger compartment, the engine can be started by briefly pressing the large Start button to the left of the steering column. Pressing it again stops the engine. QT110 IC which provides a digital output when an object is detected. In operation, the device continuously adapts to its environment and only reacts to step changes in capacitance. An output from the proximity sensor is generated by the presence of the driver’s hand at a range of approximately 80-100mm from the top rear edge of each door. The combination of a valid remote in range and the driver’s 12  Silicon Chip hand allow the door to be released. In addition, various interlocks in the code determine if door operation is permitted, based on door position, vehicle speed, ignition status, etc. Naturally, the occupants still need to manually close the doors! Starting EFIJY has a 6-litre LS2 V8 engine fitted with a supercharger. It de­ ePRNDL stands for “electronic Park Reverse Neutral Drive Low” – the electronic transmission selector located in the centre console. EFIJY uses a 4-speed GM automatic transmission, the 4L60E, with the cable control replaced by an actuator. The driver selects the gear by pushing one of the buttons located on the centre console. The buttons use the resistive encoded inputs on one of the CM4 modules, while the actuator is controlled via the H-bridge output and utilises positional feedback from both the actuator and the transmission’s internal controls. The CM4 is also responsible for siliconchip.com.au switch illumination, and selected gear position feedback, both to the driver and to other subsystems. Naturally, a number of interlocks are employed to ensure accidental operation is avoided, to prevent damage to the vehicle. Proportional speed control of the actuator is used to ensure fast response as well as accurate selection of the correct gear position Air suspension The car is fitted with integral airbag and damper assemblies and each wheel has an analog suspension height sensor. Compressed air is supplied via an onboard compressor and storage tank. A manifold with eight solenoid valves, four for lift and four for lower, together with the CM4 module, controls the air supply to each airbag to maintain the desired trim height, regardless of load in the vehicle. There are three settings: show, drive and load and the height can be controlled to within approximately 1mm. The CM4 receives the target height request from the central touch screen. Using the EEPROM in the PICAXE, the last requested suspension height is tracked to allow for system power loss. In a show vehicle, there is usually an isolator switch for the vehicle battery. This is turned off when the vehicle is in storage or on display. But because of the non-volatile memory (EEPROM) in the PICAXE, the control module knows what height it should be at when power is reapplied. The software inhibits control of height when the vehicle is moving and includes error detection and reporting. Steering column lock Setting the suspension to the show position requires the front wheels to be centred inside the front wheel arches. If this does not happen, the wheels will make contact with the fenders and result in body damage. This problem was solved using an analog steering angle sensor, similar to the type used for stability control systems. This allowed the CM4 module to determine if the steering wheel was centred and if not, allow the central display to indicate not only the need to centre the wheel but also the direction the wheel needs to be turned. When the wheel is in the correct position, a locking actuator is engaged to prevent the steering wheel being turned when siliconchip.com.au Eight high-brightness red LEDs are used in the stop indicator housing that’s mounted on the boot lid. the car is in the lowered position. The locking actuator is a rack type and requires an H-bridge to drive it to the lock and unlock positions, while integral position switches provide lock status. Again, various interlocks are employed to ensure the steering column is not allowed to lock when the vehicle is in motion. Lighting The headlamps use Osram Ostar LEDs. These consist of a cluster of five 1W LEDs mounted on a single substrate. With four of these clusters per lamp, there is approximately 20W of LED illumination per side. The outer rings contain 36 pairs of LEDs, one white 50mA device and one amber 150mA device per aperture. The tail lamps consist of 32 dual colour LEDs and a single blue 1W Dragon LED. The dual colours provide stop and tail functions by control of the current through the red elements. When a turn signal is required, the amber LEDs are strobed to provide the flash function. A 40X PICAXE running at 4MHz is used in each tail lamp assembly. LED lighting is also used for interior illumination, as well as for switches and warning lamps. Collaboration The electronic systems in EFIJY were the result of a collaboration of several departments within Holden, The tail lamps use 32 dual-colour (red and amber) LEDs to provide the stop and turn indicators. as well as a number of suppliers who contributed components or assemblies to allow EFIJY to be a fully functioning, fully-drivable demonstration of future vehicle technologies. About the author* Jeff Brown is the Technology Leader – Flexible Architecture at Holden Innovation. During his 19 years with Holden, amongst other duties, he has been responsible for powertrain management systems, vehicle networks and electrical SC systems architecture. January 2006  13