Screws cannot be operated in torque or force mode (however it is possible to obtain a similar behaviour by linking a revolute and prismatic joint programmatically), and spherical joints can only be free in torque or force mode. When dynamically enabled, a joint can be free or controlled in Force/torque, in velocity or in position. Torque or force mode: in this mode, the joint is simulated by the dynamics module, if and only if it is dynamically enabled (refer to the section on designing dynamic simulations for more information).Dependent mode: in this mode, the joint position is directly linked (dependent) to another joint position through a linear equation.sim.setJointPositon or sim.setSphericalJointMatrix). The user can however change the joint's position with appropriate API function calls (e.g. Passive mode: in this mode the joint is not directly controlled and will act as a fixed link.Ī joint can be in one of following modes: When a parent-child relationship is built between a joint and an object, the object is attached to the joint's second reference frame, thus, a change of the joint's configuration (intrinsic position) will directly be reflected onto its children. Spherical joints are always passive joints, and cannot act as motors.Ī joint is used to allow for a relative movement between its parent and its children. This does never happen with spherical joints that are internally handled to avoid this kind of situation. The analogy is however only valid while all revolute joints keep an orientation distinct from any of the two others: indeed, should two joints come close to coincide, a singular situation might appear and the mechanism might lose one DoF. In some situations, a spherical joint can be thought of as 3 concurrent and orthogonal to each other joints, that are parented in a hierarchy-chain. The three values that define a spherical joint's configuration are specified as Euler angles. Their configuration is defined by three values that represent the amount of rotation around their first reference frame's x-, y- and z-axis. Spherical joints: spherical joints have three DoF and are used to describe rotational movements (with 3 DoF) between objects.Screws can be used as passive joints, or as active joints (motors). A screw configuration is defined by one value that represents the amount of rotation about its first reference frame's z-axis. A pitch parameter defines the amount of translation for a given amount of rotation. Screws: screws, which can be seen as a combination of revolute joints and prismatic joints (with linked values), have one DoF and are used to describe a movement similar to a screw.
They can be used as passive joints, or as active joints (motors).
Their configuration is defined by one value that represents the amount of translation along their first reference frame's z-axis. Prismatic joints: prismatic joints have one DoF and are used to describe translational movements between objects.Their configuration is defined by one value that represents the amount of rotation about their first reference frame's z-axis.