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cusfkiwi.main

References

cusfkiwi.main module

References

[1] - A.M.P. Tombs, The Extended Mars Lander, Exercise 1: Euler’s equations and quaternions, September 18, 2013

class cusfkiwi.main.Simulation(body, dt, end_condition)

Bases: object

Class for running simulations and storing the resulting data.

Parameters

  • bodies (list) – Body object to add to the simulation.

  • dt (float) – Timestep.

  • end_condition (callable) – Function of the State. Must return True when the simulation needs to end.

states

List of State objects, containing the full state of the body at each timestep.

Type

list

fdot(fn, t, debug=False)
run(debug=False)
x()
Returns

x coordinates

Return type

numpy.ndarray

y()
Returns

y coordinates

Return type

numpy.ndarray

z()
Returns

z coordinates

Return type

numpy.ndarray

t()
Returns

Time values

Return type

numpy.ndarray

V()
Returns

Velocity magnitudes

Return type

numpy.ndarray

class cusfkiwi.main.Body(init_state, mass, moments_of_inertia, forces, moments)

Bases: object

Class for storing the inertial properties of a body as well as the forces and moments that are to be applied.

Parameters

  • init_state (State) – Initial conditions as a State object.

  • mass (Mass) – Mass object to represent the body’s mass.

  • moments_of_inertia (MomentsOfInertia) – MomentsOfInertia object to represent the principal moments of inertia of the body.

  • forces (list) – List of Forces objects, to represent the forces on the body.

  • moments (list) – List of Moments objects, to represent the moments on the body.

class cusfkiwi.main.State(time, pos, vel, ang_pos, ang_vel)

Bases: object

Class for storing the entire state of a body (6 degrees of freedom in total).

Parameters

  • time (float) – Time.

  • pos (list) – Position in the absolute reference frame, [x, y, z]. List or array of length 3.

  • vel (list) – Velocity in the absolute reference frame, [v_x, v_y, v_z]. List or array of length 3.

  • ang_pos (list) – Attitude in quaternion form, should be a length 4 list or array. Represents a conversion from the body reference frame to the absolute one. Can be useful to use scipy.spatial.transform.Rotation if you need help with this.

  • ang_vel (list) – Angular velocity in the body’s reference frame, [w_A, w_B, w_C]. List or array of length 3.

time

Time.

Type

float

pos

Position in the absolute reference frame, [x, y, z].

Type

list

vel

Velocity in the absolute reference frame, [v_x, v_y, v_z].

Type

list

ang_pos

Attitude in quaternion form, should be a length 4 list or array. Represents a conversion from the body reference frame to the absolute one.

Type

list

ang_vel

Angular velocity in the body’s reference frame, [w_A, w_B, w_C].

Type

list

to_array()
static from_array(array)
class cusfkiwi.main.Mass(value, input='none')

Bases: object

Class for representing the mass of a body.

Parameters

  • value (float or callable) – Mass. Either a constant or a callable.

  • input (str, optional) – “none” for a constant, “time” to receive the time as an input, “state” to receive a State object as input. Defaults to “none”.

class cusfkiwi.main.MomentsOfInertia(value, input='none')

Bases: object

Class for representing the principal moments of inertia of a body. Note that these principal moments of inertia should be given in the body’s reference frame. This makes them constant for a constant mass and geometry system.

Parameters

  • value (list or callable) – List of principal moments of inetia in the form [A, B, C]. Can be a constant, function of time, or function of the State.

  • input (str, optional) – “none” for a constant, “time” to receive the time as an input, “state” to receive a State object as input. Defaults to “none”.

class cusfkiwi.main.Force(value, input='none')

Bases: object

Class for representing the forces on a body. These must be given in the absolute reference frame (NOT the body reference frame).

Parameters

  • value (list or callable) – Force, [F_x, F_y, F_z]. List or array of length 3. Should be in the absolute (NOT body) reference frame. Either a constant or a callable.

  • input (str, optional) – “none” for a constant, “time” to receive the time as an input, “state” to receive a State object as input. Defaults to “none”.

class cusfkiwi.main.Moment(value, input='none')

Bases: object

Class for representing the moments on a body. These must be given in the body’s reference frame (NOT the absolute one).

Parameters

  • value (list or callable) – Moment, [M_A, M_B, M_C], representing components about the body’s A, B and C axes (using a right hand rule). List or array of length 3. Should be in the body reference frame (NOT the absolute one). Either a constant or a callable.

  • input (str, optional) – “none” for a constant, “time” to receive the time as an input, “state” to receive a State object as input. Defaults to “none”.