The Challenge of Designing Systems with High Levels of Autonomy

Body Design vs Autonomy

Even though autonomy features are significantly influencing consumer purchase decisions, vehicle design still dominates and plays a key role in the buying process. Most sensors (with the notable exception of Radars) including cameras, Lidars and ultrasonics require a line of sight to operate and as such are mounted on the exterior surfaces of the vehicle. However, the same property that lets these sensors view the external world (i.e., their mounting location) also makes them visible to an external observer and creates an unavoidable conflict. Design philosophies prioritize clean unbroken surfaces and as such a visible sensor placed in the middle of such a surface is considered detrimental. Consequently, there is a desire to conceal sensors from an external observer. This becomes increasingly challenging when we have to account for various body colors (Consider the challenges of concealing a camera on a black car vs a bright red one) as well as bigger sensors (higher levels of autonomy leading to longer detection range which corresponds to higher resolution and even larger optics). Some critical camera sensors are also mounted inside the cabin (typically behind the windshield) and as such their enclosure and its appearance needs to be considered in the overall design. 

As we start including active emitter sensors such as Lidars, the size grows drastically, and newer mounting positions have to be considered. Various mounting positions have been proposed lately with the mounting on the roof being the most common, however it does have a detrimental effect to the overall streamlining of the body.

In summary, the typical development flow places a greater emphasis on evaluating the sensor properties (Resolution, power, detection range etc.) without considering the aesthetics behind it which leads to multiple iterations with the studio and a longer development cycle. Involving the design studio team from the start can mitigate this problem and help in reducing the overall design cycle.

To clean or not to clean

The sensors mounted behind the windshield have an added advantage that they are not exposed to the elements, and they are typically mounted in a way such that their field-of-view cone is within the arc of the windshield wiper blades. However, sensors mounted on the exterior surfaces are not so fortunate. These sensors are susceptible to blockage due to environmental conditions such as rain drops, ice/snow or simply just dust. As we gradually transition to higher levels of autonomy, it is imperative that the sensors are maintained in impeccable operating state. A dirty /obstructed lens can cause an object detection algorithm to fail in detecting a vehicle or pedestrian leading to a dangerous driving condition. 

The need of the hour at the bare minimum is to enable monitoring functions that continuously monitor the state and health of the sensor and disable the autonomy features when an obstruction is detected. However, the user experience can vary greatly based on the expectations from the user after an obstruction is detected. Consider the example of a driver on a long road trip under adverse weather or environmental conditions (such as a dusty road). Under such conditions, the cameras may be getting soiled every 15-20 minutes, however it may be impractical to expect the driver to stop the vehicle, manually clean the sensors and continue driving especially if the frequency of occurrence is high.

To mitigate such scenarios, there is an increased effort to develop self-cleaning systems. Some of the most popular ones include using a washer nozzle solution with either liquid, air or a mix of the two, using ultrasonic vibrations, centrifugal force or even sound waves to dissipate the obstructing particles. However, each of these solutions do come with their own set of tradeoffs. Using a nozzle and washer solution can lead to increase in cost based not only on the cost of the nozzle but also the cost of the piping required to go from the fluid bottle to each of the independent sensors. Further, frequent use of the cleaning system may run the fluid bottle dry frequently thereby leading to larger bottle design which again needs to factor in the constraints of space and weight. Using ultrasonic vibrations or centrifugal based solutions solves the fluid capacity and piping issues but does lead to higher cost and larger sensor size which again violates the ‘clean’ design philosophy that focuses on creating unbroken surfaces.

Sensor cleaning continues to be an actively researched field and there is no one solution fits all. The design philosophy, user preferences and operating domain need to be factored in while selecting the optimal solution.