Page 118 - Toucpad robotics C11

Working Principle
Simple Touch Sensor (Switch-Based): Works like a push-button switch. When physical contact is made, it closes an
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electrical circuit, sending a digital signal (ON/OFF) to the robot’s controller.
Force/Pressure Sensors (Resistive/Capacitive): More advanced tactile sensors measure the amount of force or
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pressure applied.
∑ Resistive: Their electrical resistance changes when pressure is applied.
∑ Capacitive: Their electrical capacitance changes when they are pressed or touched.
These changes in electrical properties are then converted into an analogue or digital signal proportional to the
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applied force.
Arrays of Sensors: Some advanced tactile sensors are arrays of tiny individual sensors spread over a surface (like
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a robot’s fingertip or palm), allowing the robot to not just detect contact but also the shape and texture of an object,
or how pressure is distributed.
Applications in Robotics
Grasping and Manipulation: Essential for robotic grippers to detect when they have made contact with an object
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and to adjust gripping force to avoid crushing delicate items or dropping heavy ones.
Collision Detection: Detecting unexpected contact with obstacles or people to trigger a safety stop (especially
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important for collaborative robots).
Surface Following: Guiding a robot along a surface by maintaining light contact.
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Assembly Tasks: Confirming that components are properly seated or fastened by feeling the force feedback.
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Human-Robot Interaction: Enabling robots to respond to human touch, for example, a robot responding when its
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hand is held.
Advantages

Direct Interaction: Provides direct information about physical contact, pressure, and force.
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Simple for Basic Detection: Simple switch-based touch sensors are very easy to implement and cost-effective.
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Safety Enhancement: Crucial for ensuring safe interaction between robots and their environment/humans.
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Enables Delicate Tasks: Allows robots to perform tasks requiring a “sense of feel.”
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Disadvantages

Limited Spatial Resolution: Simple touch sensors only provide point contact information. Advanced arrays are better
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but more complex.
Wear and Tear: Mechanical touch sensors can degrade over time due to repeated physical contact.
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Not for Remote Sensing: Cannot detect objects from a distance; requires direct physical contact.
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Can be Fragile: Some highly sensitive force sensors can be delicate.
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Gyroscopes and Accelerometers (Often Combined in an Inertial Measurement Unit - IMU)

These two types of sensors are often found together in a single unit called an
Inertial Measurement Unit (IMU). They are crucial for a robot’s understanding of
its own motion and orientation.

Gyroscopes

Description
A Gyroscope (specifically a Micro-Electro-Mechanical Systems or MEMS gyroscope
commonly used in robotics) is a sensor that measures angular velocity, which is
the rate of rotation around an axis.

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Touchpad Robotics - XI