Feeling the Force: Pressure Sensors for More Adaptive Robotics

Introduction

For decades, industrial and service robots have relied predominantly on vision systems and inertial sensors to perceive and interact with the world around them. However, while necessary, these modalities lack a critical human sense – the sense of touch.

Robots equipped only with cameras and accelerometers cannot detect tactile physical forces, gather data on surface textures, or gain proprioceptive feedback on their movements and joint positions. Lack of tactile awareness severely limits their ability to handle objects dexterously, move adaptively through complex environments, and respond safely to physical contact.

Pressure sensors now provide robots with the vital tactile feedback needed to elevate their abilities. By continuously monitoring hydraulic and pneumatic pressures within robotic joints and actuators, pressure sensors give robots proprioceptive awareness of their own motion and torque exertion. This feedback enables advanced control of movements and the application of targeted joint forces.

Covering robot surfaces with flexible and conformable pressure sensor arrays creates an artificial sense of touch. The skin-like pressure-sensing layers allow robots to detect, map, and respond to external forces from contact, collisions, or human interaction.

Robots can achieve remarkable human-like dexterity and adaptability with sufficient pressure data integrated into control loops. Tactile pressure feedback brings robotics closer to safe and seamless collaboration alongside human coworkers in factory settings. It also opens up new horizons for robotics in high-risk environments like disaster response, defense, healthcare, and space exploration where blind automation is insufficient.

Pressure Sensor Applications in Robotics

Pressure sensors play an integral yet often underappreciated role in modern robotics. By continuously monitoring internal hydraulic/pneumatic pressures, external forces, and environmental conditions, pressure sensors provide robots with critical feedback for dexterous movement control, tactile sensing, environment interaction, and internal monitoring.

One critical application is proprioceptive sensing – using pressure measurements inside joints to determine the applied torque and forces. This information on the robot’s motion and loading allows far more precise control, greatly enhancing manipulation capabilities and stability. Tendon-driven robot designs utilize pressure sensors to measure tendon tensions, which correlates directly to the force generated at the joints. More conventional robotic methods install load cells that measure joint pressure differentials to infer the torque. Some advanced systems even mount ultra-miniaturized MEMS pressure sensors directly on robot joints for high-resolution proprioceptive feedback. This pressure-sensing strategy is analogous to biological proprioception and makes robots aware of their movement and loading conditions.

Similarly, incorporating pressure sensors into a robot’s exterior skin provides tactile feedback about contact forces. Large sensor arrays with many individual pressure sensors can map the magnitude and distribution of forces across the robot body. These arrays allow appropriate reactions to physical contact like a gentle touch or a damaging collision. Such tactile skin systems based on flexible and conformable pressure sensor matrices give robots refined environmental awareness and a human-like sense of touch.

Other environmental interactions leverage differential pressure sensors to detect collisions. Sensors can detect impending impacts by measuring pressure fluctuations inside fluid-filled bladders and help initiate bracing maneuvers. This collision-sensing approach even works for soft-bodied robots without a solid frame. By controlling contact forces, pressure sensors further help robots react safely if they or a human collide.

Internally, pressure sensors monitor many robots’ hydraulic and pneumatic systems that power movement. Abnormal pressure drops can detect leaks and prompt repairs before total failure. Flow sensors using differential pressure principles monitor pump and motor operation. Altitude and height changes are also discerned from pressure differences as the robot ascends or descends. This sensory feedback contributes to stable and reliable mobility.

Pressure sensing also enables weatherproofing of robots operating outdoors or in demanding environments. Installing micro-machined pressure sensors with waterproof membranes inside the robot body allows water ingress from rain or flooding to be rapidly detected before electronics are damaged. The robot can then take action to preserve internal components or signal for help.

Technology Innovations Driving Progress

Several key technology advances catalyze more pervasive and powerful adoption of pressure sensing in robotics.

Microelectromechanical systems (MEMS) manufacturing enables high-resolution yet extremely compact differential pressure sensors that can integrate proprioceptively into robotic joints and actuators. For example, MEMS-based pressure sensors from Superior Sensor Technology integrate advanced features such as closed-loop control, advanced digital filtering, and software-based pressure switching. These fully integrated sensors provide critical internal torque and force feedback for precise motion control and dexterous object manipulation abilities.

Additionally, flexible pressure sensor arrays printed with graphene, quantum tunneling composites, or other nanomaterials allow stretchable, conformable electronic skin layers to wrap around robot structures. Materials like nanotube-infused latex create sensor skins that stretch over complex joints and surfaces. This artificial sense of touch based on flexible printed sensors produces dense pressure mapping with high spatial resolution across the entire robot body. The skin-like precision tracking enables robots to safely detect, react, and interact with people in collaborative workspaces. 

On the data processing side, modern machine learning techniques like deep neural networks can ingest real-time pressure data from sensor arrays to optimize controls and responses. The computational models can interpret pressure patterns from proprioceptive and tactile sensors to inform manipulator movements and reflex reactions. For example, one study demonstrated using reinforcement learning on pressure input to teach a robot arm advanced dexterous manipulation skills like rolling a ball in its palm.

Finally, new soft actuators and grippers based on fluidic elastomer technology are highly reliant on pressure monitoring throughout the structure for precise control and feedback. These pneumatic soft robotics actuators with integrated pressure sensors can gently conform to grasped objects. This technology enables safer physical human-robot collaboration in shared workspaces where traditional rigid robots would be too risky.

As these various innovations progress, pressure sensing promises to become an essential integrated feedback modality embedded across future robotics, from industrial automation to medical devices. We are only beginning to glimpse the potential of responsive, adaptive robotics empowered by artificial touch sensing.

The Future Robotics: Human-Like Tactile Sensing

As pressure sensor technologies and integration continue progressing, robots enhanced with artificial touch sensing will transform many domains:

• Human-Like Dexterity: With sufficient tactile pressure data, robots can achieve remarkably human-like dexterity, manipulating objects with delicate precision across various weights, textures, and shapes. This dexterity will accelerate automation in warehousing, manufacturing, surgery, and more.
• Seamless Human Collaboration: Ultra-sensitive pressure skin will allow future robots to collaborate seamlessly and safely alongside human coworkers. Pressure feedback prevents injurious contact forces during physical interactions.
• Hazardous Environment Operation: Pressure-sensing durable robots can take on risky tasks like disaster response, deep-sea exploration, mining, and space missions where direct human involvement is dangerous. Pressure data helps robots react and adapt.
• Medical Applications: Tactile pressure sensing will enable breakthroughs in prosthetic limbs, robotic surgery, rehabilitation, and assistive robotics, where interacting safely with humans is critical.
• Smart Infrastructure: Robot inspectors covered in pressure-sensing skin could monitor bridges, oil pipelines, wind turbines, and other infrastructure. Pressure data reveals developing faults.

As costs fall and integration improves, tactile pressure sensing will likely join vision, inertial, and positional sensing as standard modalities in advanced robots. Pressure sensing promises a future where capable, helpful robots can operate productively and safely alongside humans in dynamic real-world environments.

Conclusion

Pressure sensors empower robotics with critical capabilities ranging from proprioception for dexterous manipulation to tactile sensing for responsive interactions. By continuously monitoring internal hydraulic pressures, external contact forces, and environmental conditions, pressure data allows robots to move, handle objects, and react to physical stimuli with human-like sensitivity. Ongoing advances in MEMS sensors, flexible printed arrays, and machine learning integration will drive breakthroughs in multi-modal robot perception and seamless human collaboration.

As costs fall, pressure sensing promises to become a standard feedback modality integrated into future robot designs across industrial, medical, assistive, infrastructure monitoring, and hazardous environment applications. The possibilities are vast as pressure sensors equip robots with the feedback needed to perform safely, reliably, and intelligently in the dynamic physical world.