Fraunhofer Institute for Manufacturing Engineering and AutomationOne of the major strengths of Care-O-bot 3 is its standardized and modular hardware setup. Each of the following components can be operated independently and can be plugged together by simply connecting few power and bus cables. The use of many industrial components guarantees robust and reliable functionality and a good support in case of any problems.
Omnidirectional Platform
The robot is driven by four wheels. Each wheel’s orientation and speed can be set individually. This omnidirectional drive system enables complex movements even in constrained space as well as simple control of the complete kinematic chain (platform – manipulator – gripper) control. The base also includes the battery pack, three laser scanners and a PC for navigation tasks. The mobile platform can be operated independently from the rest of the robot.
Sensor Head
The sensor head consists of a high resolution stereo rig and a 3D time-of-flight camera. It is located on a horizontal axis that allows to move the sensor head back and forth. This axis in turn is mounted on a 4 DOF manipulator, the torso, giving enough flexibility to position the cameras. The torso can also be used for body gestures, e.g. to give feedback to the user in an intuitive and natural way.
Manipulator
Care-O-bot 3 can be equipped with different lightweight arms. Existing platforms use the Schunk Lightweight Arm 3 (LWA 3) and the Kuka LBR, both providing 7 degrees of freedom (DOF). The arms can be controlled by CAN bus. The Schunk LWA has a payload of 5 kg, the Kuka LBR of 7 kg. Due to its integrated sensors the Kuka LBR is particularly sensitive.
Gripper
Care-O-bot 3 is equipped with the Schunk Dexterous Hand (SDH). The SDH offers 7 degrees of freedom and integrated tactile sensors. Each of the three fingers has two axes, and two fingers can be turned around one vertical axis. Thus different types of grasps can be performed, e.g. cylindrical, spherical, parallel grasps. The single axes and the tactile sensors can be addressed via CAN-Bus or a serial interface. The joints allow position and velocity control and force control can be easily achieved by using the tactile sensor data. The gripper is a modular component that can be attached easily to the different manipulators using a fast changer system.
Tray as interaction interface
The primary interface between Care-O-bot 3 and the user consists of a tray attached to the front of the robot, which carries objects for exchange between the human and the robot. The tray includes a touchscreen and retracts automatically when not in use. The robot arm is only used to place objects on the tray or take them away from it. It is stopped immediately as soon as people are detected in the vicinity of the robot. Combined with safety sensors for navigation this concept enables the safe operation of Care-O-bot 3 in public spaces.