Some of us are always extra cautious when we drive behind, and to the right, of a turning semi-truck. This is partially because of the Wide Turns sign typically located on the back of the truck reminding us of the risk of getting caught in the truck’s wide right turn if we drive too close.
Autonomous trucking, especially for trucks with articulated multi-piece bodies, poses unique challenges that are not felt in other industries such as autonomous passenger vehicles. One such challenge is in finding solutions to accurately and robustly determine the angle between a tractor and the trailer that it is towing.
A tractor pulling a trailer is generally more stable when travelling in a straight line than when turning. While turning, the angle between the tractor and the trailer is not a straight line but is at an angle. To safely operate a tractor towing a trailer, there may be a maximum angle whereby exceeding such an angle causes instability and may cause the tractor or trailer to roll over or jackknife. Thus, the angle between the tractor and the trailer must be accurately determined to ensure that both of them will continue to be in control.
This is an important challenge to overcome in an autonomous system as an autonomous vehicle lacks the benefit of a human driver’s judgment regarding stability of the combination of the tractor and the trailer when driving around curves.
At TuSimple, we have developed and are continuing to develop numerous solutions to this problem. Two of these solutions, that we produced years ago, were recently awarded as patents in March 2021, namely US Patent No. 10,935,378 titled “System and Method for Angle Measurement” and US Patent No. 10,942,271 titled “Determining an Angle Between a Tow Vehicle and a Trailer.” These patents cover a wide array of technical solutions, ranging from using LiDAR to ultrasonic sensors, to determine a trailer angle. To be clear, our sensor suite utilizes a camera-centric architecture that combines multiple sensors including cameras, LiDARs and radars. While we believe that long range perception enabled by our camera technology is essential for providing a long planning horizon that is required for a truck driving at 75mph on the highways, we do use LiDARs and other sensors for short range perception.
LiDAR systems use laser scanning to determine a point cloud, or a set of points that describe the sensed environment. One analogy of a point cloud is to think of throwing bouncy balls at a wall with your eyes closed. You might be able to tell roughly where on the wall the bouncy ball hit based on the direction you threw it and the time the ball came back to you. The point cloud could be thought of as your characterization of the wall based on throwing out a set of these bouncy balls.
These point clouds can be collected continuously over a period of time such that differences in these point clouds over time can be determined to characterize different or changing objects. Our “System and Method for Angle Measurement” patent describes techniques of using these point clouds to determine an angle between a tow vehicle and its trailer, such as by having LiDAR at the rear of the tow vehicle to determine the angle based on how the point cloud characterizing the trailer varies from when the tow vehicle and trailer are moving in a straight direction.
However, this patent does not stop there. An issue with using LiDAR, especially for automated trailer angle detection, is that noisy unwanted data may be present in large sets of data. For example, when turning, a side of a trailer may also be detected by a LiDAR system and thus throw off calculations of a trailer angle based on the LiDAR data from the front of the trailer. This patent also describes techniques on making trailer angle determinations more robust and efficient, such as via different techniques of filtering out unwanted noise. Having less noise means that accuracy of trailer angle determinations can be maintained or improved despite using less information.
Beyond LiDAR, there may be other promising technologies to leverage in solving this problem. Our “Determining an Angle Between a Tow Vehicle and a Trailer” patent describes using ultrasonic sensors to determine a trailer angle. Ultrasonic sensors measure distance by using ultrasonic waves that “bounce” off of a surface. This patent covers many different ways of using ultrasonic sensors for trailer angle determination. This can include a plurality of ultrasonic sensors arranged in a configuration to have a more robust determination of the trailer angle. For example, ultrasonic sensors may be oriented to illuminate a trailer with ultrasound at a perpendicular angle when the tow vehicle and trailer are not moving in a straight line. By doing so, some ultrasonic sensors may provide better distance determinations at different trailer angles. Also, having a plurality of sensors provides a level of redundancy so that a failure of certain sensors could still produce sensor data sufficient for safe operation. The data produced by these sensors can be refined to reduce noise and focus on what matters – achieving safe and reliable autonomous vehicle operation by accurate determinations of a trailer angle.
Beyond the two patents highlighted above, we have many more innovations that have moved the needle of technology. We are proud of the fact that in the first three months of 2021, we have been awarded with 33 additional patents representing double digit growth in our patent portfolio. These 33 patents solve other such problems ranging from lighting control to improve sensor perception, safety, and compliance all the way to lane change control so that our autonomous trucks can change lanes in an automated manner to avoid collisions. We are always inspired by the great work that our technical folks do to solve hard problems like these so that the promise of autonomous trucking is not a distant vision but rather something just around the next corner, a wide turn away.