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Hardware
This is a collection of descriptions of hardware components used in RoboCup@Home.
We have good experience with Ethernet/TCP-IP Axis cameras; they feature a good low-level processing which compensates for most common lighting variations, at least a first measure.
The choice is extremely wide today, and many alternatives may be considered.
As nowadays the bottleneck is usually not the hardware resolution of the image sensor, it may be worth considering a very wide-angle lens, which leaves a large margin of angular addressing freedom to the computer (Notice that fish-eyes do NOT make distorsions; it is just that as angles are wide, the probability of having at the same time close and remote objects in the same image is large. The laws of perspective apply and of course close objects appear larger than remote ones)
- Point Grey Research offers several stereo vision cameras one of which is the Bumblebee 2. It is a pre-calibrated camera with two Sony 1/3" CCD sensors providing images with 640x480 at 48 frames per second (FPS) or 1024x768 at 18FPS. It does NOT have the disparity calculation on a chip. (One such camera is used by the AllemaniACs, contact them in case of questions.)
Laser range finder provide distance information based on time of flight of IR laser beams.
- The company Lase (now owned by Sick) offers the ELD L A, a 2D laser range finder providing distance measurements in 360° with angular increments of 0.25° or 0.5°. The resolution accuracy is about 4 mm with a repeatability of below 3.0 cm. The scan frequency can either be 10 Hz or 20 Hz. (This model is used by the AllemaniACs, contact them in case of questions.)
- Sick offers the safety laser scanner S 300. It has an apex angle of 270° with an angular resolution of 0.5°. One complete scan (541 distance measurements) is acquired in 80ms (12.5Hz). The scanner has a size of (102x105x152)mm (WxLxH) and a weight of 1.2kg. As it is a model from the safety scanner series, it can not be configured via messages over the data channel (RS422). The only way to configure the scanner (measurement mode, protective/warning fields etc.) is by means of an additional rs232 link and a configuration software that only runs under MS Windows. (A S300 Professional is used by the team b-it-bots, contact them in case of questions.)
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Sick offers the 2D laser range finder LMS 200 and the LMS 291 both providing an apex angle of up to 180° with angular resolutions of 1°, 0.5° and 0.25°. Both sensors can be configured to provide remission values, i.e. the reflectivity of an object in addition to its distance. When configured to operate in continuous sending mode over the complete 180° with a resolution of 1° and without remission values, the scanner's measurement frequency is 75Hz. (A Sick LMS 200 is used by the team b-it-bots, contact them in case of questions.)
Fraunhofer IAIS sells both the LMS 200 and the LMS 291 mounted on mechanical actuators to gain an additional degree of freedom, i.e. 3D laser scanner (-> http://www.3d-scanner.net). - Hokuyo has been traditionnally selling convenient, small laser scanners (ca 5cm side), with about 1cm of accuracy at 4 m. max., on a 240 degree range, with about 700 radii. USB port. Now they are expanding their offer.
Ultrasonic Range Finders are among the most popular sensors for object detection and avoidance, using sonar beams. They differ in directivity and most popular range finders now have directivity between 14 to 72 degrees.
- Robotic Electronics (Devantech) is almost most popular company about ultrasonic range finders, have about 6 different range finders now, which is used in some teams this 2 years. The most important trait of Devantech are low cost and high performance.
We (RH3-Y) have been using Baumer Electric industrial-grade, ultrasonic sensors (ca. 40-270 cm). Very reliable, if used alone. When several sensors are used simultaneously, risks of interference are serious.
See Also: List of Motor Controllers
We (RH3-Y) are typically using Maxon motors and Galil motion control cards for wheels. Care must be taken for a synchronous motion of both wheels. Accuracy on the order of one per thousand can be expected on common floors.
Fiveco controllers are used for arm and hand control (current, force, acceleration, speed, position, etc.).
Motion laws are typically trapezoidal in speed. Low-level servoing is typically of PID type, occasionnally with speed and force a priori terms.
At programming level, cartesian coordinates and homogeneous matrices are used for pose definition and trajectory planning. A point-arrow graphical representation of frames and transforms allows for the convenient use of tool transforms and frame computations (camera, laser sensors, arm, hand, robot, home, etc.) for advanced programmers. Users with less experience benefit in Piaget framework of convenient primitives. E.g. "PassFromCameraCoordinatesToWorldCoordinates(int TargetRow, int TargetColumn, location &TargetPosition)" is a common and straightforward Piaget primitive to be used anywhere on flat floors.
Inverse kinematic computation and coordination parametrization is done on the supervisory computer.
- Robotis sells Dynamixel servo actuators, which are configurable via an RS-485 bus. They are used in many humanoid robots.
- Neuronics AG, Switzerland offers an anthropomorphic robotic arm called Katana. It provides up to six degrees of freedom and has a maximum payload of 500g while only having a weight of 4.3kg. (A Katana6m is used by the AllemaniACs, contact them in case of questions.)
- Robai, USA produces the Veta series of 7 DOF ligth-weight robotic arms. It has a maximum payload of 350g and a maximum reach of 0.48m, and comes with a wide variety of choice for control: software provided by Robai, the Actin-SE API, or individual motor control via USB.
- Kinova inc, Canada offers modular lightweight robot arms. One of their robot arms, MICO, is a 6 DOF manipulator with a 70 cm reach and a 1.25 kg payload. The compact design and embedded controller are giving the arm a total weight of only 5 kg. It includes torque, position, current, acceleration and temperature sensors in every actuators that can all rotate without limitation. The arm is easy to integrate to a mobile platform and will not drag out all its battery power, with an average consumption of only 20W.
In order to be able to command the robot from a larger distance wireless microphones are a useful mean.
Often, wired microphones, installed over the robot, are not used as often, as the motors and fans inside the robot are a noise source that requires additional pre-processing. In addition, reverberation and ambient noise are prone to cause performance-declines in Speech Recognition. However, if the intention is to have a service robot that will interact with humans in a social environment, it is important to consider keeping the microphones installed over the robot to act as "ears", and overcome the aforementioned issues.
From the hardware side, directional microphones can be used to filter out surrounding ambient noise by "focusing" on the frontal cone of the microphone and cancel out everything else. The RODE VideoMic is an interesting choice for this purpose, as it already provides a mount to reduce the internal noise of the robot leaking in (usually used for mobile video cameras), and its directionality is comparable to high-end shotgun microphones. One is used by the Golem Team.
From the software side, see the Audio and Speech sections in Software for more information.
To communicate with the robot via another computer often WiFi is used.
- Segway offers the Segway RMP as a platform for mobile robotics applications.
- ActivMedia Robotics is selling the PeopleBot as a base for service or performance robots. It offers a gripper, table-sensing IR's and a pan-tilt-camera.
- Fraunhofer IAIS is selling a modular robot platform called VolksBot. It has been desigend for rapid prototyping and allows for easy access to and replacement of components such as motors, batteries and electronics. (The robot of the teams b-it-bots and NimbRo are based on Volksbot, contact them in case of any questions.)
- iRobot Roomba has an open API. Team NimbRo constructed an omnidirectional robot base with four individually steerable Roombas.
- REEM, developed and commercialized by PAL Robotics, is a robust, robotics research platform very suited for the RoboCup@Home competition. It is integrated into ROS, it is able to navigate autonomously, grasp objects, recognize people and speech, and has already taken part the competition as the REEM@IRI's RoboCup@Home platform.
- NimbRo-OP, developed and commercialized by University of Bonn, is a medium-sized open-source humanoid robot for research.
- VolksBot Robot construction kit developed by IAIS Fraunhofer and used by the IAIS/BIT @Home team.