Loads (Forces and Torques)

In order to model internal as well as external forces and torques, the concept of LoadElements has been introduced. In the following all LoadElements are described which are currently available.

loads

class pymbs.input.mbs_system.AddLoad(world)

Class that provides functions to create load elements

CmpForce(symbol, CS1, CS2, CSref=None, name=None)

Use addLoad.CmpForce to add a vectorial force, acting between two coordinate systems. The force, specified with respect to the parent or reference frame, acts in positive direction on the parent coordinate system (CS1) and in negative direction on the child coordinate system.

Parameters:

  • CS1 (Coordinate System, Body or MbsSystem.) – Reference to parent coordinate system / parent frame.

  • CS2 (Coordinate System, Body or MbsSystem.) – Reference to child coordinate system / child frame.

  • symbol (Expression as returned by addInput, addExpression or addSensor.) – Symbol representing a three dimensional vector variable whose components are interpreted as force values in x, y, and z-direction. The direction of x,y and z is given by the parent frame (CS1) or by the reference frame (CSref).

  • CSref (Coordinate System, Body or MbsSystem.) – Reference to reference coordinate system / reference frame.

  • name (string) – A name may be assigned to each force. If no name is given, then a name like load_1 is generated automatically. The name is used for code generation only, i.e. the symbols connected with this force will contain the name.

Returns:

Reference to the generated LoadElement

Return type:

LoadElement

CmpTorque(symbol, CS1, CS2, CSref=None, name=None)

Use addLoad.CmpTorque to add a vectorial torque, acting between two coordinate systems. The torque, specified with respect to the parent or reference frame, acts in positive direction on the parent coordinate system (CS1) and in negative direction on the child coordinate system.

Parameters:

  • CS1 (Coordinate System, Body or MbsSystem.) – Reference to parent coordinate system / parent frame.

  • CS2 (Coordinate System, Body or MbsSystem.) – Reference to child coordinate system / child frame.

  • symbol (Expression as returned by addInput, addExpression or addSensor.) – Symbol representing a three dimensional vector variable whose components are interpreted as torque values around the x, y, and z-axis. The direction of x,y and z is given by the parent frame (CS1) or by the reference frame (CSref).

  • CSref (Coordinate System, Body or MbsSystem.) – Reference to reference coordinate system / reference frame.

  • name (string) – A name may be assigned to each force. If no name is given, then a name like load_1 is generated automatically. The name is used for code generation only, i.e. the symbols connected with this force will contain the name.

Returns:

Reference to the generated LoadElement

Return type:

LoadElement

Joint(symbol, joint, name=None)

Use addLoad.Joint to add a torque, acting on a joint. In case of a translational joint, a force has to be supplied. In case of a rotational joint, the load represents a torque.

Parameters:

  • joint (Joint.) – Reference to joint.

  • symbol (Expression as returned by addInput, addExpression or addSensor.) – Symbol representing a scalar. Force or Torque depending on whether it is a translational or rotational joint.

  • name (string) – A name may be assigned to each force. If no name is given, then a name like load_1 is generated automatically. The name is used for code generation only, i.e. the symbols connected with this force will contain the name.

Returns:

Reference to the generated LoadElement

Return type:

LoadElement

PtPForce(symbol, CS1, CS2, name=None)

Use addLoad.PtPForce to add a scalar force, acting between two coordinate systems along a connecting line. A positive force means that the coordinate systems are pushed apart.

Parameters:

  • CS1 (Coordinate System, Body or MbsSystem.) – Reference to parent coordinate system / parent frame.

  • CS2 (Coordinate System, Body or MbsSystem.) – Reference to child coordinate system / child frame.

  • symbol (Expression as returned by addInput, addExpression or addSensor.) – Symbol representing a scalar variable whose value is taken as force between the two coordinate systems.

  • name (string) – A name may be assigned to each force. If no name is given, then a name like load_1 is generated automatically. The name is used for code generation only, i.e. the symbols connected with this force will contain the name.

Returns:

Reference to the generated LoadElement

Return type:

LoadElement