Joints

Tutorials

Reading a joint position from sensor

To read a joint position for a specific joint:

// Assume joints is of type nao_sensor_msgs::msg::JointPositions
joints.positions[nao_sensor_msgs::msg::JointIndexes::HEADYAW]

nao_sensor_msgs::msg::JointPositions contains an array of joint positions for all joints of the NAO. The indexes for each joint are stored as constants in nao_sensor_msgs::msg::JointIndexes.

Writing a joint position command

To populate the message,

• Append index of the joint to the indexes vector

• Append position of the joint to the positions vector

For example:

// Assume joints is of type nao_sensor_msgs::msg::JointPositions
nao_command_msgs::msg::JointPositions command;

command.indexes.push_back(nao_command_msgs::msg::JointIndexes::HEADYAW);
command.positions.push_back(0.2);

Note

Joint indexes are stored as constants in nao_command_msgs::msg::JointIndexes.

Iterating over all joints

To iterate over all joints, use a for loop that iterates NUM_JOINTS times to iterate over all joints, as following:

// Create JointStiffness command with stiffness 1.0 for all joints
nao_command_msgs::msg::JointStiffnesses command;

for (unsigned i = 0; i < nao_command_msgs::msg::JointIndexes::NUMJOINTS; ++i)
{
    command.indexes.push_back(i);
    command.positions.push_back(1.0);
}

Joint Indexes

A msg file that defines the indexes of joints as constants. Used in indexes for Sensor Joint Msgs and Command Joint Msgs.

This msg does not have any fields, and doesn’t serve a purpose in transmitting any information on topics.

The following list are the joint indexes copied from JointIndexes.msg:

uint8 HEADYAW=0
uint8 HEADPITCH=1
uint8 LSHOULDERPITCH=2
uint8 LSHOULDERROLL=3
uint8 LELBOWYAW=4
uint8 LELBOWROLL=5
uint8 LWRISTYAW=6
uint8 LHIPYAWPITCH=7
uint8 LHIPROLL=8
uint8 LHIPPITCH=9
uint8 LKNEEPITCH=10
uint8 LANKLEPITCH=11
uint8 LANKLEROLL=12
uint8 RHIPROLL=13
uint8 RHIPPITCH=14
uint8 RKNEEPITCH=15
uint8 RANKLEPITCH=16
uint8 RANKLEROLL=17
uint8 RSHOULDERPITCH=18
uint8 RSHOULDERROLL=19
uint8 RELBOWYAW=20
uint8 RELBOWROLL=21
uint8 RWRISTYAW=22
uint8 LHAND=23
uint8 RHAND=24
uint8 NUMJOINTS=25

Note

Currently, there are two identical copies of Joint Indexes msg file, in the Sensor Msgs and Command Msgs package. This is because we haven’t found a nice way to avoid duplication. Possibly, this shouldn’t even be a msg file but should be just a plain hpp file.