robot Package¶

`joints` Module¶

Module of all the classes related to physical joints. These are objects that link 2 bodies together.

There are two base abstract classes for all joints: Joint and ActuatedJoint. They are not coupled (at all) with ODE or any other physics or collision library/engine.

The classes that implement at least one of those interfaces are these:

Fixed
Rotary
Universal
BallSocket
Slider

There is also an auxiliary class: JointFeedback.

class ActuatedJoint(world, inner_joint, body1=None, body2=None)[source]¶

Bases: ars.model.robot.joints.Joint

A joint with an actuator that can exert force and/or torque to connected bodies.

This is an abstract class.

Constructor.

Parameters:	world (`physics.base.World`) – inner_joint (`ode.Joint`) – body1 (`physics.base.Body`) – body2 (`physics.base.Body`) –

class BallSocket(world, body1, body2, anchor)[source]¶

Bases: ars.model.robot.joints.Joint

Constructor.

Parameters:	world (`physics.base.World`) – body1 (`physics.base.Body`) – body2 (`physics.base.Body`) – anchor (3-tuple of floats) – joint anchor point

class Fixed(world, body1, body2)[source]¶

Bases: ars.model.robot.joints.Joint

Constructor.

Parameters:	world (`physics.base.World`) – body1 (`physics.base.Body`) – body2 (`physics.base.Body`) –

class Joint(world, inner_joint, body1=None, body2=None)[source]¶

Bases: object

Entity that links 2 bodies together, enforcing one or more movement constraints.

This is an abstract class.

Constructor.

Parameters:	world (`physics.base.World`) – inner_joint (`ode.Joint`) – body1 (`physics.base.Body`) – body2 (`physics.base.Body`) –

body1[source]¶

body2[source]¶

class JointFeedback(body1, body2, force1=None, force2=None, torque1=None, torque2=None)[source]¶

Bases: object

Data structure to hold the forces and torques resulting from the interaction of 2 bodies through a joint.

All attributes are private. The results (force1, force2, torque1, torque2) are all length-3 tuples of floats.

Constructor.

Parameters:	body1 (`physics.base.Body`) – body2 (`physics.base.Body`) – force1 (3-tuple of floats) – force2 (3-tuple of floats) – torque1 (3-tuple of floats) – torque2 (3-tuple of floats) –

body1[source]¶

body2[source]¶

force1[source]¶

force2[source]¶

torque1[source]¶

torque2[source]¶

class Rotary(world, body1, body2, anchor, axis)[source]¶

Bases: ars.model.robot.joints.ActuatedJoint

Constructor.

Parameters:	world (`physics.base.World`) – body1 (`physics.base.Body`) – body2 (`physics.base.Body`) – anchor (3-tuple of floats) – joint anchor point axis (3-tuple of floats) – rotation axis

add_torque(torque)[source]¶

Apply torque about the rotation axis.

Parameters:	torque (float) – magnitude

angle[source]¶

Return the angle between the two bodies.

The zero angle is determined by the position of the bodies when joint’s anchor was set.

Returns:	value ranging `-pi` and `+pi`
Return type:	float

angle_rate[source]¶

Return the rate of change of the angle between the two bodies.

Returns:	angle rate
Return type:	float

set_speed(speed, max_force=None)[source]¶

Set rotation speed to speed.

The joint will set that speed by applying a force up to max_force, so it is not guaranteed that speed will be reached.

Parameters:	speed (float) – speed to set max_force (float or None) – if not None, the maximum force the joint can apply when trying to set the rotation speed

class Slider(world, body1, body2, axis)[source]¶

Bases: ars.model.robot.joints.ActuatedJoint

Joint with one DOF that constrains two objects to line up along an axis.

It is different from a Piston joint (which has two DOF) in that the Slider does not allow rotation.

Constructor.

Parameters:	world (`physics.base.World`) – body1 (`physics.base.Body`) – body2 (`physics.base.Body`) – axis (3-tuple of floats) – rotation axis

add_force(force)[source]¶

Apply a force of magnitude force along the joint’s axis.

position[source]¶

Return position of the joint with respect to its initial position.

The zero position is established when the joint’s axis is set.

Return type:	float

position_rate[source]¶

Return position’s time derivative, i.e. “speed”.

Return type:	float

class Universal(world, body1, body2, anchor, axis1, axis2)[source]¶

Bases: ars.model.robot.joints.Joint

Constructor.

Parameters:	world (`physics.base.World`) – body1 (`physics.base.Body`) – body2 (`physics.base.Body`) – anchor (3-tuple of floats) – joint anchor point axis1 (3-tuple of floats) – first universal axis axis2 (3-tuple of floats) – second universal axis

`sensors` Module¶

Module of all the classes related to sensors.

There are base classes for sensors whose source is a body, joint or simulation. It also considers those which read information automatically by subscribing to certain signals.

Some abstract classes are:

BaseSourceSensor
BaseSignalSensor
BodySensor
JointSensor
SimulationSensor

Some practical sensors are:

RotaryJointSensor, JointTorque
Laser
GPS, Velometer, Accelerometer, Inclinometer
KineticEnergy, PotentialEnergy, TotalEnergy, SystemTotalEnergy

It also contains the auxiliary classes SensorData and SensorDataQueue.

class Accelerometer(body, time_step)[source]¶

Bases: ars.model.robot.sensors.BodySensor

Calculate and retrieve a body’s linear and angular acceleration.

Warning

The provided time_step is used to calculate the acceleration based on the velocity measured at two instants in time. If subsequent calls to on_change are separated by a simulation time period different to the given time_step, the results will be invalid.

class ActuatedJointSensor(joint)[source]¶

Bases: ars.model.robot.sensors.JointSensor

Sensor whose source of data is an ActuatedJoint joint.

class BaseSignalSensor(sender=_Any, autotime=False)[source]¶

Bases: object

Base class for sensors that handle signals with on_send().

Constructor.

Parameters:	sender – object that will send the signal; if it is `any_sender`, subscription will be to any object autotime – if True and `_get_time()` is not overriden, every measurement’s time will set to the computer time in that instant

any_sender = _Any¶

on_send(sender, *args, **kwargs)[source]¶

Handle signal sent/fired by sender through the dispatcher.

Takes care of building a data object, set time to it and save it in the data_queue.

Parameters:	sender – signal sender args – signal arguments kwargs – signal keyword arguments

sender[source]¶: Return the sender of the signal to which the sensor listens.

class BaseSourceSensor(source)[source]¶

Bases: object

Abstract base class for all sensors.

Sensor data is stored in a queue (data_queue), and it is usually retrieved after the simulation ends but can be accessed at any time:

measurement = sensor.data_queue.pull()

Warning

Beware that ars.utils.containers.Queue.pull() returns the first element of the queue and removes it.

get_measurement()[source]¶: Return a measurement of the sensor packed in a data structure.

on_change(time=None)[source]¶

Build a SensorData object and stores it in the data_queue.

Parameters:	time (number or None) – if None, current (computer’s) time is used

source[source]¶

class BodySensor(body)[source]¶

Bases: ars.model.robot.sensors.BaseSourceSensor

Abstract base class for sensors whose source of data is a body.

body[source]¶

class GPS(body)[source]¶

Bases: ars.model.robot.sensors.BodySensor

Retrieve a body’s XYZ position.

class Inclinometer(body)[source]¶

Bases: ars.model.robot.sensors.BodySensor

Retrieve a body’s pitch and roll.

class JointForce(sim_joint, sim)[source]¶

Bases: ars.model.robot.sensors.SingleSignalSensor

Sensor measuring force ‘added’ to a joint.

signal = 'robot joint post add force'¶

class JointPower(sim_joint, sim)[source]¶

Bases: ars.model.robot.sensors.MultipleSignalsSensor

Sensor measuring power applied by a joint (due to force and torque).

signals = ['robot joint post add torque', 'robot joint post add force']¶

class JointSensor(joint)[source]¶

Bases: ars.model.robot.sensors.BaseSourceSensor

Abstract base class for sensors whose source of data is a joint.

joint[source]¶

class JointTorque(sim_joint, sim)[source]¶

Bases: ars.model.robot.sensors.SingleSignalSensor

Sensor measuring torque added to a joint.

signal = 'robot joint post add torque'¶

class KineticEnergy(body)[source]¶

Bases: ars.model.robot.sensors.BodySensor

Retrieve a body’s kinetic energy, both due to translation and rotation.

$E_t &= \frac{1}{2} m v^2 = \frac{1}{2} m \cdot v^\top v \\ E_r &= \frac{1}{2} I \omega^2 = \frac{1}{2} \omega^\top \mathbf{I} \omega$

class Laser(space, max_distance=10.0)[source]¶

Bases: ars.model.robot.sensors.BaseSourceSensor

Laser scanner.

get_ray()[source]¶

on_change(time=1386948660.133477)[source]¶

set_position(pos)[source]¶

Set position of the ray.

Useful mainly when it is not attached to a body.

Parameters:	pos (3-sequence of floats) – position

set_rotation(rot)[source]¶

Set rotation of the ray.

Useful mainly when it is not attached to a body.

Parameters:	rot (9-sequence of floats) – rotation matrix

class MultipleSignalsSensor(signals, *args, **kwargs)[source]¶

Bases: ars.model.robot.sensors.BaseSignalSensor

Abstract base class for sensors subscribed to multiple signals.

Constructor.

Parameters:	signals (iterable) – signals to subscribe to

class PotentialEnergy(body, gravity)[source]¶

Bases: ars.model.robot.sensors.BodySensor

Retrieve a body’s potential energy.

Calculated based on the current position (x) and world’s gravitational acceleration (g).

$E_p = m \cdot g \cdot h = - m \cdot g^\top x$

class RotaryJointSensor(joint)[source]¶

Bases: ars.model.robot.sensors.ActuatedJointSensor

Sensor measuring the angle (and its rate) of a rotary joint.

class SensorData(*args, **kwargs)[source]¶

Bases: object

Data structure to pack a sensor measurement’s information.

get_arg(index)[source]¶

get_args()[source]¶

get_kwarg(key)[source]¶

get_kwargs()[source]¶

get_time()[source]¶

set_time(time)[source]¶

class SensorDataQueue[source]¶

Bases: ars.utils.containers.Queue

Queue-like container for sensor measurements.

class SimulationSensor(sim)[source]¶

Bases: ars.model.robot.sensors.BaseSourceSensor

Abstract base class for sensors whose source of data is a simulation.

Constructor.

Parameters:	sim (`ars.model.simulator.Simulation`) – simulation

sim[source]¶

Return the simulation object.

Returns:	simulation
Return type:	`ars.model.simulator.Simulation`

class SingleSignalSensor(signal, *args, **kwargs)[source]¶

Bases: ars.model.robot.sensors.BaseSignalSensor

Abstract base class for sensors subscribed to one signal.

Constructor.

Parameters:	signal – signal to subscribe to

class SystemTotalEnergy(sim, disaggregate=False)[source]¶

Bases: ars.model.robot.sensors.SimulationSensor

Retrieve a system’s total potential and kinetic energy.

It considers all bodies in the simulation. The kinetic energy accounts for translation and rotation.

$E_p &= m \cdot g \cdot h = - m \cdot g^\top x \\ E_k &= \frac{1}{2} m \cdot v^\top v + \frac{1}{2} \omega^\top \mathbf{I} \omega$

class TotalEnergy(body, gravity, disaggregate=False)[source]¶

Bases: ars.model.robot.sensors.BodySensor

Retrieve a body’s potential and kinetic energy.

The kinetic energy accounts for translation and rotation.

$E_p &= m \cdot g \cdot h = - m \cdot g^\top x \\ E_k &= \frac{1}{2} m \cdot v^\top v + \frac{1}{2} \omega^\top \mathbf{I} \omega$

class Velometer(body)[source]¶

Bases: ars.model.robot.sensors.BodySensor

Calculate and retrieve a body’s linear and angular velocity.

`signals` Module¶

This module contains string values defining different signals related to the ars.model.robot package.

robot Package¶

joints Module¶

sensors Module¶

signals Module¶

`joints` Module¶

`sensors` Module¶

`signals` Module¶