Sensing

Sensing Overview

Sensing enables you to perform analytical tasks on a model. For example, you can perform inverse kinematic analyses of a robotic manipulator model. By prescribing the end-effector trajectory and sensing the joint actuation forces and torques, you can obtain the time-varying profile of each joint actuation input.

The variables you prescribe, the model inputs, and those you sense, the model outputs, determine which types of analysis you can perform. By changing the model inputs and outputs, you can perform numerous other analysis types. For example, to perform forward kinematic analysis on the robotic manipulator model, you can prescribe the manipulator joint trajectories and sense the resulting end-effector trajectory.

Variables You Can Sense

To support various analytical tasks, Simscape™ Multibody™ software provides a wide range of variables that you can sense. Each variable belongs to either of two categories:

• Motion variables — Linear and angular position, velocity, and acceleration. Linear variables are available in different coordinate systems, including Cartesian, spherical, and cylindrical. Angular variables are available in different formats, including quaternion, axis-angle, and transform matrix.

• Force and torque variables — Actuation, constraint, and total forces and torques acting at a joint, as well as certain forces and torques acting outside of a joint.

Blocks with Sensing Capability

The entire sensing capability spans multiple Simscape Multibody blocks. Two types of blocks provide motion sensing:

• Joint blocks — Motion sensing between the base and follower port frames of a joint block. Variables that you can sense are organized by joint primitive (prismatic, revolute, or spherical).

• Transform Sensor block — Motion sensing between any two frames in a model. This block provides the most comprehensive motion sensing capability in Simscape Multibody.

Three types of blocks provide force and torque sensing:

• Joint blocks — Actuation, constraint, and total force and torque sensing between the base and follower port frames. Actuation force and torque sensing is arranged by joint primitive.

• Constraint blocks — Constraint force and torque between the base and follower port frames.

• Certain Forces and Torques blocks — Total force the block exerts between the base and follower port frames. Only certain Forces and Torques blocks provide this type of sensing, such as the Spring and Damper Force and Inverse Square Law Force.

Sensing Output Format

Each sensing output is in a physical signal format. You can convert physical signals into Simulink^® signals using Simscape converter blocks, e.g., for plotting purposes using the Scope block. For information on how to use physical signals in Simscape Multibody models, see Actuating and Sensing with Physical Signals.