Using Sensors: Effort Sensor

Learning Objectives

This tutorial introduces how to use an effort sensor for sensing a joint effort in Omniverse Isaac Sim. After this tutorial, you will know how to add a effort sensor to the scene, activate, and measure acceleration, angular velocity, and orientations in a scene

10-15 Minute Tutorial

Getting Started

Prerequisites

• Review the Core Tutorial series a prior to beginning this tutorial.

This tutorial demonstrates how to integrate the effort sensor into an Omniverse Isaac Sim simulation, by going over the method to create the effort sensor, modify effort sensor properties, and read effort sensor data.

Effort Sensor Properties

1. enabled parameter determines if the sensor is running or note.

2. sensor period parameter specifies the time inbetween sensor measurement. A sensor period that’s lower than the physics delta time will always output the latest physics data. The sensor frequency cannot go beyond the physics frequency.

3. use_latest_data parameter will make the sensor always use the latest simulation data if enabled.

4. dof parameter stores the index of the joint measured. The recommended way to update it is by calling update_dof_name(dof_name=name_of_the_joint) function.

5. data_buffer_size parameter stores the size of the data buffer used in user’s custom interpolation function. The recommended way to update it is by calling change_buffer_size(new_buffer_size=size_of_buffer).

Creating and Modifying the effort sensor

The effort sensor can be created using a python class. The only required parameters is the prim path of the specific joint that the sensor measures from.

from omni.isaac.sensor.scripts.effort_sensor import EffortSensor
import numpy as np

sensor = EffortSensor(
    prim_path="/Articulation/Arm/RevoluteJoint",
    sensor_period=0.1,
    use_latest_data=False,
    enabled=True
)

To modify sensor parameters, you can change class member variables like sensor_period, use_latest_data, and enabled directly, and for changing the dof_name and buffer_size for the readings, please use the corresponding member functions update_dof_name and change_buffer_size.

Reading Sensor Output

get_sensor_reading(self, interpolation_function = None, use_latest_data = False)

the get sensor reading function takes in two parameters: an interpolation function (optional) to use in place of the default linear interpolation function, and use latest data flag (optional) for retrieving the data point from the current physics step if the sensor is running at a slower rate than physics rate. The function will return an EsSensorReading object which contains is_valid, time, and value

Sample usage to get the reading from the current frame:

from omni.isaac.sensor.scripts.effort_sensor import EffortSensor

# create a new effort sensor
sensor = EffortSensor(
    prim_path="/Articulation/Arm/RevoluteJoint",
    sensor_period=0.1,
    use_latest_data=False,
    enabled=True
)

# get sensor reading
reading = sensor.get_sensor_reading(use_latest_data = True)

Sample usage with custom interpolation function:

from omni.isaac.sensor.scripts.effort_sensor import EffortSensor, EsSensorReading


# Input Param: List of past EsSensorReading, time of the expected sensor reading
def interpolation_function(data, time):
    interpolated_reading = EsSensorReading()
    # do interpolation
    return interpolated_reading

# create a new effort sensor
sensor = EffortSensor(
    prim_path="/Articulation/Arm/RevoluteJoint",
    sensor_period=0.1,
    use_latest_data=False,
    enabled=True
)

# get sensor readings
reading = sensor.get_sensor_reading(interpolation_function)

Isaac Read Effort Node

For reading effort sensor data using the Omnigraph, see this tutorial: Effort Sensor Node.

API Documentation

See the API Documentation for complete usage information.