MATLAB Classes for Simscape Multibody Enhancements: Programmatically specify joint primitive actuations and compute joint primitive accelerations
You can now programmatically specify actuation forces or torque for joint primitives of a compiled multibody model, compute the corresponding dynamics of the model, and measure the resulting accelerations of desired joint primitives.
You can specify actuation forces or torque for the prismatic, revolute, and
spherical joint primitives. To specify the actuations, use the simscape.multibody.JointActuationDictionary structure with the simscape.multibody.PrismaticPrimitiveActuationForce, simscape.multibody.RevolutePrimitiveActuationTorque, and simscape.multibody.SphericalPrimitiveActuationTorque classes. To
compute the dynamics of the model based on the specified actuations, use the computeDynamics method.
After computing the dynamics of the model, you can use the jointPrimitiveAcceleration method to measure the accelerations of the
prismatic, revolute, spherical, constant velocity, and lead screw joint primitives
in the model. The outputs follow the SI unit conventions.
Custom Tire Force and Torque Block: Model custom tires
You can use the Custom Tire Force and Torque block to create custom tire models for off-road or on-road scenarios. To model a custom tire, use the output signals from the block to compute the tire force and torque and then feed the computed signals back to the block as inputs. You must compute the tire force and torque with respect to the contact frame of the tire. The tire force must have nonnegative value, otherwise the Custom Tire Force and Torque block clips the force to zero. In addition, you must ensure the units of the force and torque are consistent during the simulation.
The Custom Tire Force and Torque block has two
methods to determine the contact point and normal. For a rough ground surface, such
as off-road scenarios or speed bumps, set the Contact Frame Computation
Method parameter to Weighted Penetration.
To avoid computational challenges due to the rough surface, the block computes
equivalent planes of the rough surface by using the weighted penetration normal
method. The block uses the equivalent planes to determine the contact point and
normal.
If you set Contact Frame Computation Method to
Closest Point, the block uses the same method that
the Magic Formula Tire
Force and Torque block uses to determine the contact point and
normal.
Joint Block Enhancement: Lock the degrees of freedom of joints
You can now lock the degrees of freedom of these joints:
A locked joint keeps a constant position and has zero velocity. The constraints introduced from a locked joint contribute to the constraint force and torque in the joint.
To lock a joint at its assembled position throughout a simulation, under the
Mode Configuration section, set Mode
to Locked. You can also use an input signal to lock a
joint during a simulation. For example, if the input signal of the
mode port is 1, the joint becomes
locked. To enable the mode port, in the block dialog box, under
the Mode Configuration section, set Mode
to Provided by Input.
The simulation returns an error if you use these settings for a locked joint:
Under the Actuation section, set the
Force or Torque parameter
to Automatically Computed.
Under the Actuation section, set the
Motion parameter to Provided by
Input.
Spatial Contact Force Block Enhancement: Measure the rotation matrices of the contact frames of a point cloud
You can now measure the rotation matrices of the contact frames of a point cloud. The output is a 3-D array that has N 3-by-3 matrices, where N equals the number of points in the point cloud. Each 3-by-3 matrix of the array is the rotation matrix of the corresponding contact frame with respect to the reference frame. The reference frame can be the reference frame of either the base or follower geometry of the Spatial Contact Force block. If a point is not in contact with the other geometry, the corresponding matrix is an identity matrix.
Featured Examples
Ratchet Pawl Mechanism — Learn how to model a ratchet with a locking pawl. Planar contact modeling geometry is used to streamline computation.
Measure Inertial Properties of Multibody Systems — Learn how to how to measure the inertial properties, such as mass and center of mass, of a multibody mechanism or a specific body group.