A Flexible Multimodal Sole Sensor for Legged Robot Sensing Complex Ground Information during Locomotion

Abstract

Recent achievements in the field of computer vision, reinforcement learning, and locomotion control have largely extended legged robots’ maneuverability in complex natural environments. However, little research focuses on sensing and analyzing the physical properties of the ground, which is crucial to robots’ locomotion during their interaction with highly irregular profiles, deformable terrains, and slippery surfaces. A biomimetic, flexible, multimodal sole sensor (FMSS) designed for legged robots to identify the ontological status and ground information, such as reaction force mapping, contact situation, terrain, and texture information, to achieve agile maneuvers was innovatively presented in this paper. The FMSS is flexible and large-loaded (20 Pa–800 kPa), designed by integrating a triboelectric sensing coat, embedded piezoelectric sensor, and piezoresistive sensor array. To evaluate the effectiveness and adaptability in different environments, the multimodal sensor was mounted on one of the quadruped robot’s feet and one of the human feet then traversed through different environments in real-world tests. The experiment’s results demonstrated that the FMSS could recognize terrain, texture, hardness, and contact conditions during locomotion effectively and retrain its sensitivity (0.66 kPa−1), robustness, and compliance. The presented work indicates the FMSS’s potential to extend the feasibility and dexterity of tactile perception for state estimation and complex scenario detection.

Accessorizing Quadrupedal Robots with Wearable Electronics

“…With the recent progress in locomotion control of quadrupedal robots, there have been efforts to accessorize the robots with sensors to improve their locomotion by expanding their environment perception [5][6][7][8] and to acquire mission-specific data. [5,9,10] Actuators can also be integrated with robots to handle objects and provide sensory output.…”

“…[16,20,25,26] Furthermore, implantable tactile sensors can inform quadrupedal robots of the ground condition, allowing them to calculate important quantities such as the center of mass and zero-moment point. [7] As illustrated in Figure 1c, Aoyagi et al developed an arrayed capacitive tactile sensor, which was then integrated with the sole of a legged robot for real-time 3D force detection. [27] The sensor consists of two rubber hemispheres, between which there is an array of capacitive sensing elements, whose capacitance value changes with applied pressure.…”

“…Tactile sensing films are based on various mechanisms-including piezoresistivity, [7,[46][47][48][49] triboelectricity, [7] piezocapacitance, [50][51][52] and triboelectricity [7,53,54] -to accurately map contact force and hence provide insights into force distribution and surface texture. Piezoresistivity refers to the change in the electrical resistivity of a material in response to a mechanical strain.…”

“…Depending on the specification of the wearable sensors, it is possible to integrate more than one sensing element on one device (see Figure 5b). [7,68] In this case, multiple sensing elements can be interfaced with an MCU, which usually comes with multiple internal analog-to-digital converter (ADC) modules and a BLE module. This way, the number of modules used and the total peripheral circuit area can be reduced.…”

Progress in the Triboelectric Human–Machine Interfaces (HMIs)-Moving from Smart Gloves to AI/Haptic Enabled HMI in the 5G/IoT Era

“…With the gradual rollout of AI technology around the world, intelligent robots will play a more important role in our society and will gradually replace humans in laborintensive or dangerous tasks, from the industries of service, manufacturing and medical, to daily life assistant, as well as future scientific-related space exploration [198]. As the medium to perceive the external world and enhance the interactions with humans, sensors based on TENGs have also been investigated a lot to mimic the bionic sensory system for robots' tactile sensing [199][200][201][202][203], gesture/motion monitoring [204,205], gait analysis [206], etc., thanks to their good compatibility brought by TENGs' wide material choices.…”