Leading automotive test solution supplier AB Dynamics, together with sister company Dynamic Research, Inc. (DRI), has launched a next-generation pedestrian ADAS target, the Soft Pedestrian 360™. It has been developed to support tests for improved sensor perception and categorisation as well as significantly decrease the time and cost of testing through improved robustness.
To enhance the realism of the target the Soft Pedestrian 360 features sophisticated articulation of the knee, hip, shoulder and neck. Actively articulated knees, enabling the hip and knee to move independently of each other, control the gait and allow a greater and more varied range of movement to be reproduced than is possible from a passive system. This is critical for vehicle sensor systems to ensure the correct categorisation of a pedestrian.
“Properly representing the stance phase of the gait, when the foot is stationary relative to the ground, can be a critical factor in an AEB system’s categorisation of the target as a pedestrian,” said Joseph Kelly, Chief Engineer at Dynamic Research, Inc. “Without this attribute, an AEB system could miscategorise the target as something other than a pedestrian and react differently. The team at DRI researched gait characteristics to identify and recreate the correct knee and hip articulation angles as functions of percent of gait cycle.”
The gait is automatically synchronised with the position, speed and acceleration of the target relative to a starting point using the platform’s IMU (Inertial Measurement Unit). This method prevents a phenomenon that the team has termed as “Flintstoning”, where the foot in the stance portion of the gait is not stationary relative to the ground and results in better characterisation.
“Damage to the vehicle under test caused by targets can be a substantial contributor to the total cost of testing ADAS technologies,” said Kelly. “It isn’t just the damage to the test vehicle but also lost track and engineering time waiting for repairs that substantially increase the cost of testing. For example, if a windshield is damaged, camera systems located behind it often require recalibration, which is time-consuming and costly. We have specifically designed the Soft Pedestrian 360 to minimise the risk of damage to the test vehicle.”
The key to reducing the potential for damage to the test vehicle are the target’s compliance, the minimisation of external hardpoints and the modularity of the design, which reduces the mass of any individual component that could contact the test vehicle and cause damage. The limbs, head and mounting pole attach to the torso via foam blocks that engage corresponding sockets in the torso, such that when these components separate on impact, there are no exposed hard points.
The servos operating the limbs and the head of the pedestrian are also completely encased in foam and sit within each component. This means that the vehicle under test is protected when the limbs are disconnected upon impact.
The durability of the product has been improved using a novel slipper clutch that stops the servos from being back-driven during a collision avoiding damage. The target is also covered in a hard-wearing fabric clothing that prevents the foam core from being worn away or torn apart, maintaining a consistent shape throughout testing. The clothing can be easily and cost-effectively replaced should it become damaged.
“Efficient use of track time is critical to keeping costs down and maximising the uptime of both the test vehicle and the test equipment is a critical part of this,” said Kelly. “Before we developed our own pedestrian target, we were regularly changing and repairing servos as a result of damage and this significantly impacted the test schedule. Our solution aims to make ADAS testing as efficient as possible.”
The Soft Pedestrian 360’s modular design provides operators with increased testing flexibility. The articulating arms and head can be swapped for static units, for example when conducting Euro NCAP tests where articulation isn’t required. This provides a simplified and cost-effective configuration option when active articulation isn’t required but provides the opportunity to increase realism where necessary.
The limbs and head can also be easily changed to increase the variety of testing. For example, the prescriptive head used for NCAP and NHTSA tests can be changed for an active unit for development work or the arms changed to represent a pedestrian using a cell phone.
This next-generation pedestrian target has been designed and engineered by AB Dynamics Group company Dynamic Research, Inc. in California. The company provides research and testing services for the world’s leading OEMs, completing hundreds of tests per year, including FMVSS, NHTSA NCAP and Euro NCAP tests. DRI has leveraged its extensive hands-on experience with test targets and equipment to design, develop, and produce a range of best-in-class surrogate targets, such as the Soft Car 360™.
“DRI’s experience working with the world’s leading safety organisations and OEMs has been critical in the development of the Soft Pedestrian 360,” said Kelly. “Everything we have learned from the hundreds of tests conducted annually has gone into the design and development of the product to reduce test vehicle damage and improve the efficiency of testing. As with all of our products, it has been designed by test engineers, for test engineers.”
SOURCE: AB Dynamics
