Sensors & Actuators

Sensors and actuators are integral components of exoskeleton technology, enabling the detection of user movements and external forces and facilitating the desired mechanical actions of the exoskeleton. Here's an overview of sensors and actuators commonly used in exoskeletons:

Sensors:

1. Joint Angle Sensors: These sensors measure the angles and positions of the user's joints, providing information about the user's limb position and movement. Examples include potentiometers, encoders, or inertial measurement units (IMUs) that incorporate accelerometers, gyroscopes, and magnetometers.

2. Force Sensors: Force sensors detect the forces exerted by the user or external environments. They provide information about the interaction forces between the user's limb and the exoskeleton, enabling force feedback, control, and safety features. Force-sensitive resistors, load cells, or strain gauges are commonly used force sensors.

3. Electromyography (EMG) Sensors: EMG sensors detect and measure the electrical activity of muscles. They provide information about the user's muscle activation patterns, which can be used to trigger specific actions or control the exoskeleton. EMG sensors are often placed on the user's skin over targeted muscles.

4. Tactile Sensors: Tactile sensors are used to detect contact or pressure between the user's limb and the exoskeleton or external objects. They can provide feedback regarding contact forces, pressure distribution, or object recognition. Tactile sensors can utilize technologies such as resistive or capacitive touch sensors, piezoelectric sensors, or force-sensitive resistors.

5. Inertial Sensors: Inertial sensors, such as accelerometers and gyroscopes, measure linear and angular accelerations and rotations. They provide information about the user's motion, orientation, and balance. Inertial sensors are often used in combination with other sensors to estimate joint angles or detect changes in the user's posture.

Actuators:

1. Electric Motors: Electric motors, such as brushed or brushless DC motors, are commonly used as actuators in exoskeletons. They provide rotational or linear motion, generating the forces and torques required for joint movements and assistance. Electric motors offer controllability, compactness, and the ability to generate high torque outputs.

2. Pneumatic/Hydraulic Actuators: Pneumatic or hydraulic actuators utilize compressed air or fluid to generate force and motion. These actuators can provide high power output, compliance, and controllability. Pneumatic or hydraulic actuators are often used in applications where high forces or quick responses are required.

3. Shape Memory Alloys (SMAs): SMAs are smart materials that can change shape in response to temperature or electrical stimuli. SMAs can be used as actuators in exoskeletons, providing lightweight and compact actuation. They are often used in applications where small-scale actuation or fine-tuning of forces is needed.

4. Cable-Driven Systems: Cable-driven systems use cables or tendons connected to electric motors to transmit forces and create movement. These systems offer lightweight and flexible actuation, enabling natural joint movements and reducing the weight of the exoskeleton.

The specific sensors and actuators used in an exoskeleton depend on factors such as the application, desired functionality, size, weight, power requirements, and cost considerations. Advanced sensor fusion techniques, combining data from multiple sensors, are also employed to enhance the accuracy and robustness of the measurements and control in exoskeleton systems.