Global Research Innovation Platform “GRIP”
This is the second post in a three-part series on key elements of TRI’s Human Interactive Driving technologies.
Motivation
At TRI, we prioritize cutting-edge research, but we’re also focused on demonstrating how advanced capabilities work on real platforms. This allows us to bridge the gap between research and product development by learning how to integrate new technologies on physical platforms.
To maximize efficiency, it’s critical to minimize development overhead. This approach is a key factor in rapidly advancing studies on physical platforms.
Simulation
Simulation test benches, including Software-In-the-Loop (SIL) and Hardware-In-the-Loop (HIL), are excellent initial options for rapid research trials. As seen in Figure 1, they require low integration effort, but the fidelity of the experience for the user is not as high. No matter how good a simulation is, it will never be like driving a real car.
Motion Simulator
Motion simulators, like the TRI Driver-in-the-loop Motion Simulator, occupy a unique middle ground between simulations and vehicle platforms. They excel in conducting complex environmental tests, such as urban driving and multi-agent scenarios, and offer the flexibility to integrate new hardware and software easily. However, there are limitations in the fidelity of vehicle motion and passenger view when compared to actual vehicles. This can be a drawback for research that requires higher fidelity testing of vehicle maneuvers.
Production Car-based Platform
Vehicle platforms built on production vehicles are the most common and have the highest fidelity experiences but require a tremendous integration effort. The main challenge stems from these vehicles being optimized for mass production and cost efficiency, making it hard to modify and integrate new technology. Therefore, modification of production-based platforms to make them suitable for research is ideal during the earlier phases of research, where rapid prototyping requires fast yet significant changes to vehicle hardware and software.
Drivable Test Bench
Therefore, there is still a big gap in research platform capabilities as we move research development from the Motion Simulator to Production Vehicles. Specifically, there is no platform that has the realism of a Production Vehicle with the ease of rapid prototyping seen in the Motion Simulator. To bridge this gap, we proposed creating a “drivable test bench.” The bench is equipped with hardware and software that can be easily updated. We call it the ‘Global Research Innovation Platform,’ or ‘GRIP’ for short. With GRIP, we envision the seamless integration of research findings into Toyota’s product lineup, with our test bench serving as a key conduit, facilitating the transfer and support of research innovations.
What’s new?
Over-actuated
‘Over-actuated’ refers to having additional controls beyond those found in standard passenger cars. Our platform features fully decoupled front and rear steering, along with independent wheel acceleration and brake torque controls. This setup allows us to simulate a variety of vehicle maneuvers, such as wheel slip, understeer, and oversteer, on different road surfaces, ranging from high to low friction. This capability significantly reduces logistics efforts, as it obviates the need to transport test vehicles to proving grounds with specific surface conditions.
Rolling Chassis
The ‘rolling chassis’ design — a vehicle framework without bodywork — facilitates the rapid integration of prototype Human-Machine Interface (HMI) devices. In our context, HMI encompasses visual, audio, and human input devices (like steering wheels, pedals, joysticks, etc.). Integrating these devices into standard passenger vehicles usually requires considerable effort. However, their installation onto a rolling chassis is remarkably straightforward.
Design Principles
Electric
Given the growing popularity of Battery Electric Vehicles (BEVs), we chose GRIP to be an all-electric platform, making it ideally suited to accelerate the internal development of technologies for Toyota’s BEV strategy. We chose in-wheel motors, which are packaged in the wheel unit themselves, to drive the vehicle. These in-wheel motors allow us to control the torque on each wheel more quickly and effectively and expand the vehicle capabilities that our advanced vehicle control systems can demonstrate. Beyond giving us expanded vehicle dynamics capabilities, in-wheel motors have the additional advantages of simplifying our powertrain design, increasing the space in the vehicle for easier future modification, and even being simpler to model in software.
Safety
Safety is always our top priority, and the main additional risk created by an electric powertrain is the risk due to exposure to high-voltage batteries. To minimize this in a flexible, research-oriented platform, we chose a 100V battery system over higher voltage options like the common 400V system. This lower voltage system, coupled with proper Personal Protective Equipment (PPE) and safety protocols, enables us to move quickly yet safely while modifying and integrating new technology into the vehicle. The lower voltage does limit the powertrain’s torque output but is still sufficient for us to reach speeds of around 60 mph.
Update Friendly
This aspect is crucial for a test bench. As mentioned earlier, using a rolling chassis simplifies hardware updates, including adding new devices and connecting wire harnesses. From a software standpoint, a centrally controlled system architecture facilitates testing new control concepts. We centralized intelligent vehicle dynamics control functions, like skid control and lane trace control, in the central computers, simplifying software modifications.
Current Research
As described in the previous Medium blog on “Driving Sensei: Unlocking Driving Mastery with AI” (https://medium.com/toyotaresearch/driving-sensei-87e049e5d2bc), “low-μ emulation” was selected as a first trial to validate the vehicle platform capability. Low-μ emulation is a feature in GRIP that simulates the behavior of a vehicle on low-traction surfaces, such as wet roads or snow or ice, even though the car is actually on dry asphalt. One of the reasons why ordinary people cannot address low-traction conditions is that they don’t have the opportunity to experience them because cars are designed not to make it happen. As GRIP has over-actuated capabilities, it can give drivers many options to experience them safely, and drivers can improve their skills on how to address them.
What’s next?
In addition to the mechanical advancements, integrating cutting-edge augmented reality and virtual reality (AR/VR) features into GRIP could potentially take its research capabilities to unprecedented levels. The AR/VR features will overlay virtual visual effects onto GRIP’s real-world vehicle maneuver emulation. By blending virtual elements with physical maneuvers, researchers will be able to simulate complex driving scenarios and environmental conditions with a level of realism and control previously unattainable.
The AR/VR integration in GRIP stands to not only enhance the fidelity of research simulations but also to open doors to innovative studies that were previously hindered by technological limitations. This advancement promises a significant leap forward in automotive research, offering an unparalleled tool for exploring and discovering the field.
