Robotics Glossary

I would like this glossary of robotics terms to grow. If you have some terms you would like to see added please email them to me.

acceleration-level - Mathematical formulations working with the change in joint speeds with respect to time. Integrating accelerations twice provides displacements. See position-level and velocity-level.
analytical methods - Purely mathematical methods that do not require iteration.
autonomous - Operating without pre-programmed behaviors and without supervision from humans.
biomimetic - Mimicking natural biology
closed-form - A problem formulation that does not require iteration for its solution.
conservative motion - A path where both the end-effector and the joints repeatedly follow their same respective trajectories.
degrees of freedom - The number of independent variables in the system. Each joint in a serial robot represents a degree of freedom.
dexterity - A measure of the robot's ability to follow complex paths.
direct search - A method of solving problems numerically using sets of trial solutions to guide a search. The search is direct because it does not explicitly evaluate derivatives.

dynamics - The study of forces that cause motion
dynamic model - A mathematical model describing the motions of the robot and the forces that cause them.
end-effector - The robot's last link. The robot uses the end-effector to accomplish a task. The end-effector may be holding a tool, or the end-effector itself may be a tool. The end-effector is loosely comparable to a human's hand.
end-effector space - A fixed coordinate system referenced to the base of the robot.
equality constraint - A restriction that requires the displacement or motion of the robot to equal a specified value. Equality constraints specify the position and orientation of the robot's end-effector.
error function - The error function assigns a single value that represents the difference between the desired and actual values of one or several dependent variables.
fully constrained robot - A robot with as many independent joints as there are equality constraints on the placement of the end-effector.
inequality constraint - A restriction that limits the value of a dependent or independent variable. Inequality constraints limit the robot's joint travels Ooint limits), joint speeds (speed limits), and torques, (torque limits).
inverse kinematics - The inverse kinematics problem is to find the robot's joint displacements given position and orientation constraints on the robot's end-effector.
iteration - Repeatedly applying a series of operations to progressively advance towards a solution.
Jacobian - The matrix of first-order partial derivatives. For robots, the Jacobian relates the end- effector velocity the joint speeds.
joint space - A coordinate system used to describe the state of the robot in terms of it's joint states. Inverse kinematics may also be thought of as a mapping from end-effector space to joint space.
kinematics - The study of motion without regards to the forces that cause those motions
kinematic influence coefficients - These coefficients describe the total influence the N input joints have on the motion of the robot and allow a direct statement of the complex and coupled nonlinear differential equations controlling the response of the system.
LaGrange multipliers - A mathematical technique for transforming equality constraints into performance criteria, thus expressing a constrained problem as an unconstrained problem.
linearly dependent - A correspondence between quantities or functions that can be described by simply adding, subtracting, or multiplying a scalar.
normalize - Scaling a number of factors so that they will be of similar magnitudes.
numerical methods - Iterative methods of solving problems on a computer. Numerical methods may have an analytical basis or they may involve heuristics. optimization - Calculating the independent variables in a function so as to generate the best function value for a given set of conditions. Optimization usually involves maximizing or minimizing a function.
performance criteria - Measures based on kinematic and dynamic models of the robot useful for evaluating the state of the robot.
plant description - A kinematic and dynamic model of the robot.
position-level - Mathematical formulations working with the joint displacements. See acceleration-level and velocity-level.
pseudoinverse - A simple method of inverting a matrix that is not square. As commonly applied to redundant robots, the pseudoinverse minimizes the two-norm of the joint speeds.
redundancy - More independent variables than constraints.
repeatability - The variability of the end-effector's position and orientation as the robot makes the same moves under the same conditions (load, temp, etc.)
resolved-rate - An extremely simple inverse kinematics method at the velocity-level.
scale - Changing magnitude by linear operation, i.e. multiplying by a scalar.
self-motion - The robot's ability to move it's intermediate links while holding the placement of the end-effector constant.
serial robot - A serial robot is a single chain of joints connected by links.
singularity - A position in the robot's workspace where one or more joints no longer represent independent controlling variables. Commonly used to indicate a position where a particular mathematical formulation fails.
statics - The study of forces that do not cause motion
two-norm - The square root of the sum of the squares. The magnitude of a vector.
velocity-level - Mathematical formulations working with the joint speeds. Integrating the joint speeds once provides the displacements. See acceleration-level and position-level.
workspace - The maximum reach space refers to all of the points the robot can possibly reach. The dexterous workspace is all of the possible points the robot can reach with an arbitrary orientation. The dexterous workspace is usually a subspace of the maximum reach space.

Source: www.learnaboutrobots.com

Robotic in Space

At right we see a press photograph of the Sojourner mobile robot that ultimately explored the surface of Mars. This is more of an R/C car than a robot as it was completely remote controlled from Earth, but NASA calls it a robot so I will too. In any case, the pictures it provided from the Martian surface were breath taking. Sometimes I think that really cool pictures may be NASA's greatest contributions. The deep field images produced by the Hubble telescope are in my opinion some of the greatest wonders of mankind.

The Sojourner is a 6-wheeled vehicle of a rocker bogie design which allows the traverse of obstacles a wheel diameter (13cm) in size. Each wheel is independently actuated and geared (2000:1). The front and rear wheels are independently steerable, providing the capability for the vehicle to turn in place. The vehicle has a top speed of 0.4m/min. It is powered by a 0.22sqm solar panel comprised of 13 strings of 18, 5.5mil GaAs cells each. The normal driving power requirement for the microrover is 10W.

NASA decided to develop a $288-million Flight Telerobotics Servicer (FTS) in 1987 to help astronauts assemble the Space Station, which was growing bigger and more complex with each redesign. Shown here is the winning robot design by Martin Marietta, who received a $297-million contract in May 1989 to develop a vehicle by 1993. About the best thing that can be said for the FTS project was that it generated a lot of lessons learned. The robot never flew and never will fly because it was never completed. This project demonstrated that fault-tolerance gone wild will doom a robot. The robot had so many redundant systems that there was just too much to go wrong.

Source: www.learnaboutrobots.com

Robotic in Nucklear

The folks working on the first atomic bombs pretty much defined telerobotics in this country. They had no other way of working with the radioactive materials. They used pure mechanical coupling for their telerobotics. The operator would stand on one side of a thick, leaded glass window while the robot manipulated the material on the other side. Cables, bands and tubes provided the coupling. Before long, these systems were carefully engineered with counter balancing and very low friction surfaces. The mechanical coupling provided natural force feedback. I had the opportunity to use one of these systems at Oak Ridge National Lab and it was far superior to any modern, motorized, electronic telerobotic system I have tried (and I have tried very many of them). I would recommend the use of these manual systems in any telerobotic application where it is not necessary to project the control beyond the next room.

The robot at right was developed for the decontamination and dismantlement of nuclear weapons facilities. It has two six-degree of freedom Schilling arms mounted on a five-degree of freedom base. As the facilities used to develop our country's nuclear weapons enter their 50th year and beyond, we now have to dismantle them and safely store the waste. The radioactive fields makes this activity too hazardous for human workers so the use of robotics makes sense. The idea for this robot is that it can hold a part in one hand and use a cutting tool with the other; basically stripping apart the reactor layer by layer (something like peeling an onion). As the robot works it too will become contaminated and radioactive and ultimately need to be stored as radioactive waste.

The graphic at left is a conceptual depiction of a robot arm mounted on a mobile base checking drums filled with radioactive waste for leaks. The question of what to do with our radioactive waste is a hotly debated topic. The idea of storing it in warehouses and monitoring it with robots for the next 100,000 years (if necessary) makes sense to me. We might as well admit we have it, monitor it logically and hope that future generations will figure out something to do with it; perhaps re-reacting it into a less dangerous state. Another proposed alternative is to bury it; which to me seems insane. Over the course of centuries it is bound to leak from its containers and ultimately into the ground water. Because it would be buried and almost impossible to monitor, we would not know about the contamination until the damage was huge, and then it would be extremely difficult to get at because it was buried. Another proposal is to use space craft and launch the material into the Sun. Who thinks of these things? Please don't mess with the Sun!

Source: www.learnaboutrobots.com

Robotic in Military

Pretty much by definition, the military is a dangerous place for humans. This makes it a logical application for robotics, but I definitely have mixed feelings about that. I can live with robots assisting soldiers, but automated killing is taking it too far. At left we see the Smart Crane Ammunition Transfer System being developed by the Robotics Research Corporation. The goal is for one soldier to be able to unload the entire truck without ever leaving the cab. The system includes cameras, video screens, force sensors and special grippers.

The photo at right shows a robotic mine-sweeper. It is basically a tractor with a bunch of swinging chains mounted on the front. These chains pound the ground with significant forces to explode any buried mines. Using GPS and relatively simple control algorithms, robots such as these can be programmed to methodically cover large areas of ground in a perfect grid. Vehicles like this can also be equipped with water cutting tools to cut into and through explosive ordnance, water cannons to disperse unruly mobs and charge setters to explode suspicious packages. For these operations the unmanned vehicle would be teleoperated.

The Predator shown at left has probably become our military's most famous unmanned vehicle. It is essentially a super high-tech r/c plane though it does have some autonomous flying capabilities. Originally designed for reconnaissance, it now can be outfitted with a variety of different weaponry, most recently the laser-guided AGM-114 Hellfire anti-armor missiles. It is roughly 29 feet long with a 49 foot wingspan. Since 1995, the Predator has seen action over Iraq, Bosnia, Kosovo and Afghanistan.

Source: www.learnaboutrobots.com

Research Robotic

The Robotics Research Corporation of America produced this robot in 1988 for NASA to study the possibility of using robots to perform maintenance on the International Space Station. Each of the robot's arms has 7 joints and they are mounted on a torso with 3 joints, giving the robot a total of 17 degrees of freedom. As discussed on the industrial robots page, a robot only needs 6 joints in general to arbitrarily position a rigid body in space. This robot's arms are called redundant arms because they have seven joints. The extra joints enable the robot to perform many tasks in an infinite number of different ways - just like human arms. For example, he can reach around obstacles. The single serial chain (the torso) branching into two separate chains (each arm) makes this robot an excellent test bed for development of kinematic optimization algorithms.

Two of these robots were produced, but only one remains intact. It is in use by the University of Texas Robotics Research Group.

ASIMO may be the most recognizable of robots around these days. I could not decide whether to put this robot on the learnaboutrobots research page or on the entertainment page. Honda calls ASIMO a research robot, so I'll call him that too.

ASIMO stands for Advanced Step in Innovative Mobility. It is 4 feet high and it can move a lot like we do, with 26 degrees of freedom. That means being able to move 26 different joints in 26 different directions. It can move forward and backward while maintaining balance. The Honda engineers who have been working on ASIMO have concentrated on making it move in our world so it could be useful to help the elderly or wheel-chair-bound. ASIMO can answer the door, pick up a phone or get the newspaper. It is often on tours designed to get young people excited about science and engineering.

A number of researchers have embraced the idea of miniature robots working together in swarms. Doug Adkins and Ed Heller developed the robot at left at Sandia National Lab. At 1/4 cubic inch and weighing less than an ounce, it is possibly the smallest autonomous untethered robot ever created. Powered by three watch batteries, it rides on track wheels and consists of an 8K ROM processor, temperature sensor, and two motors that drive the wheels. Enhancements being considered include a miniature camera, microphone, communication device, and a chemical micro-sensor.

Source: www.learnaboutrobots.com

Undersea Robotic

Undersea operations are a great application for robotics to replace humans. Working underwater is both dangerous and difficult for humans. Schilling Robotics makes the system shown at left. This system combines a remote operated vehicle with thrusters for maneuvering and two robot arms for manipulating. Note that one of the arms is almost a grappler. It can grab something rigid, such as the base of an oil rig, to steady the vehicle while the other arm performs such tasks as welding and valve maintenance.

The robot at right is a biomimetic (mimicking biology) lobster developed by the Northeastern University Marine Science Center. Biomimetic robots may employ myomorphic actuators, which mimic muscle action; neuromorphic sensors, which, like animal sensors, represent sensory modalities such as light, pressure, and motion in a labeled-line code; biomimetic controllers, based on the relatively simple control systems of invertebrate animals; and autonomous behaviors that are based on the actual animal's behavior. If a robot like this goes walking around on the ocean floor, I wonder if a big fish will eat it?

The Australian Centre for Field Robotics at the University of Sydney developed the robot shown at left as a prototype for autonomous underwater robots that may one day explore and monitor the Great Barrier Reef. At present this robot (called Oberon) must remain tethered to a ship on the surface, but its inventors predict that within a decade it would be possible for robots to be lowered to the ocean floor and left to get on with mapping the terrain on their own. Oberon has two scanning sonars and a depth sensor as well as a color camera. It does not need any independent information, such as from global positioning system satellites, to work out where it is

Source: www.learnaboutrobots.com