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¶

body2¶

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¶

body2¶

force1¶

force2¶

torque1¶

torque2¶

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¶

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¶

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¶

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¶

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¶: 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¶

class BodySensor(body)[source]¶

Bases: ars.model.robot.sensors.BaseSourceSensor

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

body¶

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¶

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=1488287192.895709)[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¶

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¶