What Is an Industrial Robot, Really?
At its core, an industrial robot is a programmable mechanical arm. Someone teaches it a sequence of positions and actions, and it repeats that sequence—exactly the same way, thousands of times—without getting tired, distracted, or bored.
A complete Yaskawa robot system has three main parts:
The manipulator (the arm): This is the part most people picture when they hear “robot.” It’s the physical arm with joints and motors that moves through space.
The controller (the brain): A cabinet—usually about the size of a small refrigerator—that contains the computer, power electronics, and motor drives. It runs the programs and tells each motor exactly where to go.
The pendant (the remote): A handheld device that the programmer uses to move the robot, write programs, and monitor what’s happening. Think of it as the robot’s remote control and programming interface rolled into one.
The Robot’s Joints: S, L, U, R, B, T
Most Yaskawa Motoman robots have six joints (also called axes). Unlike most robot manufacturers who simply number them 1 through 6, Yaskawa gives each axis a letter that describes what it does. This actually makes them easier to remember once you know the system.
Think of the robot arm like a simplified version of a human arm. Starting from the base (the “waist”) and working up to the tool (the “hand”):
| Axis | Full Name | What It Does | Human Analogy |
| S | Swivel (Base) | Rotates the entire robot left and right | Standing in place and turning your whole body left or right |
| L | Lower Arm | Swings the lower arm forward and backward | Reaching your whole arm forward or pulling it back toward your body |
| U | Upper Arm | Raises or lowers the upper arm | Bending your elbow to raise or lower your forearm |
| R | Arm Roll | Rotates the forearm along its length | Rotating your forearm so your palm faces up, then down |
| B | Wrist Bend | Tilts the wrist up and down | Bending your wrist to look at your watch |
| T | Tool Flange | Spins the tool mounting point | Rotating your hand as if turning a doorknob |
Why six axes? Six is the magic number for full flexibility in 3D space. Three axes control where the tool goes (position: left/right, forward/back, up/down), and three axes control how the tool is oriented (rotation: tilt, pan, roll). With six axes, the robot can reach a point from virtually any angle—much like how your arm can hold a coffee cup upright, sideways, or upside-down while keeping it in the same spot in space. |
How the Robot Knows Where It Is
The Concept of Coordinate Systems
When a person says “move the robot to the left,” an obvious question arises: left relative to what? The answer depends on which coordinate system you’re using. A coordinate system is simply a frame of reference—a set of directions that the robot uses to interpret movement commands.
This is exactly like giving driving directions. “Turn left” means different things depending on which way you’re currently facing. Coordinate systems solve this problem by defining a fixed set of directions.
Yaskawa robots support several coordinate systems. Here are the most common ones:
| Coordinate System | How the Robot Moves | Everyday Analogy |
| Joint | Each axis moves independently. Press a button and one specific joint rotates. | Like moving one finger at a time. Simple, but the tip of the tool follows a curved path. |
| World (Cartesian) | The tool tip moves in straight lines along X (left/right), Y (forward/back), or Z (up/down) relative to the robot’s base. | Like moving a computer mouse on a desk—you slide it left, right, forward, or back in a flat plane. |
| Tool | The tool tip moves relative to whatever tool is attached. Z+ is usually along the tool’s pointing direction. | Imagine holding a flashlight: “forward” means wherever the flashlight is pointing, regardless of which way you’re facing. |
| User | Movement follows a custom reference frame that the programmer defines—for example, aligned to a work table or fixture. | Like placing a ruler on a tilted surface and saying “move 5 inches along this ruler.” The ruler defines the directions. |
You don’t need to memorize these. The key takeaway is that the same robot can be moved in different ways depending on which frame of reference the programmer selects. The robot’s physical capabilities don’t change—only the way the human thinks about and commands the motion.
Types of Programmed Movement
When a programmer creates a robot job (program), they choose how the robot should travel between each taught position. There are three fundamental movement types:
| Movement Type | INFORM Command | What Happens | When It’s Used |
| Joint Move | MOVJ (Move Joint) | All joints move simultaneously to reach the target. The path is curved and unpredictable, but it’s the fastest way to get from A to B. | Moving between work zones, returning to a home position, or anytime the path doesn’t matter—only the destination. |
| Linear Move | MOVL (Move Linear) | The tool tip travels in a perfectly straight line from one point to the next. The controller calculates how all six joints need to coordinate to achieve this. | Welding a straight seam, applying adhesive along an edge, or approaching a part from a specific direction. |
| Circular Move | MOVC (Move Circular) | The tool tip follows an arc or circle through a set of defined points. | Welding around a curved joint, cutting a circular hole, or following any rounded contour. |
A simple way to think about it Joint Move is like walking across a room however you want—you take whatever path is natural. Linear Move is like walking along a tightrope—you must stay on the straight line. Circular Move is like walking along a curved track—you follow the arc exactly. |
Speed and Precision
Two important concepts govern all robot motion:
Speed: How fast the robot moves. During programming (Teach mode), speed is limited to keep people safe. During production, the robot runs at full programmed speed, which can be very fast—some axes can exceed 1,000 degrees per second.
Repeatability: How precisely the robot returns to the same point every time. Yaskawa robots are incredibly consistent, typically returning to within ±0.01 to 0.06 millimeters of the taught position—far more precise than any human could achieve by hand.
Operating Modes: Teach, Play, and Remote
A Yaskawa robot operates in one of three modes. These modes control who or what is in charge of the robot’s motion and are a critical part of the safety system.
| Mode | What It Means | Who Uses It |
| Teach | The robot moves only when a person manually holds down the enable switch and presses a motion button. Speed is limited for safety. This is used for programming and setup. | Robot programmers, technicians, and engineers during setup and job creation. |
| Play | The robot runs its stored program (job) at production speed. It cycles through taught positions automatically. An operator presses Start on the pendant. | Operators or technicians verifying a program before going fully automatic. |
| Remote | An external system (usually a PLC) tells the robot when to start, stop, and which job to run. This is the normal production mode. The pendant is not required to start the robot. | The production system itself. No human needs to press any buttons—the cell runs automatically. |
The mode is selected by a physical key switch on the controller cabinet. This is intentional—switching between modes is a deliberate action, not something that happens by accident.
How a Robot Learns Its Task: Teach and Playback
Yaskawa robots learn through a process called teach and playback. Here’s how it works at a high level:
1. A programmer manually moves the robot to each position it needs to visit, using the pendant to jog the arm into place.
2. At each position, the programmer saves (records) the point by pressing a button. The controller stores the exact joint angles or coordinates.
3. Between the saved points, the programmer specifies how to move (joint, linear, or circular) and how fast.
4. Additional instructions are added as needed: open a gripper, turn on a welder, wait for a signal from a conveyor, call another program, etc.
5. The resulting sequence is saved as a job on the controller. The robot can now replay this job—identically—as many times as needed.
This is why the process is called “teach and playback.” The programmer teaches the robot what to do, and the robot plays it back in production. Some more advanced methods exist (offline programming with simulation software, for example), but teach and playback remains the foundation of how most Yaskawa robots are programmed.
Glossary of Common Terms
Here’s a quick reference for terms you might hear in meetings, on the production floor, or in Yaskawa documentation:
| Term | What It Means |
| Axis (Joint) | A single point of rotation on the robot. A standard 6-axis robot has six joints, each driven by its own servo motor. |
| Controller | The cabinet that houses the robot’s computer, power supplies, and motor drives. It’s the “brain” that interprets programs and sends commands to the motors. |
| Degrees of Freedom (DOF) | The number of independent ways a robot can move. A 6-axis robot has 6 DOF, meaning it can position and orient a tool anywhere within its reach. |
| Enable Switch (Deadman) | A spring-loaded switch on the back of the pendant. In Teach mode, the operator must hold it in the middle position for the robot to move. Releasing it or squeezing it fully cuts servo power immediately. |
| End Effector / Tool | Whatever is mounted to the end of the robot arm: a welding torch, a gripper, a camera, a suction cup, etc. |
| Home Position | A predefined “parking” position where the robot rests when not working. It’s typically a tucked-in pose that keeps the robot clear of the work area. |
| I/O (Input/Output) | Electrical signals the robot uses to communicate with other equipment. Inputs tell the robot about the outside world (“part is present”); outputs tell the outside world what the robot is doing (“gripper closed”). |
| Job | A stored program on the controller that contains a sequence of instructions (movements, I/O commands, logic). The robot executes jobs to perform its task. |
| Payload | The maximum weight the robot can carry at its tool flange, including the weight of the tool itself. |
| PLC | Programmable Logic Controller. The industrial computer that manages the overall production cell. It often tells the robot when to start and stop via I/O signals. |
| Reach | The maximum distance from the robot’s base to the tip of its tool. Determines how far the robot can extend. |
| Repeatability | How precisely the robot returns to the same position each time. Yaskawa robots typically achieve repeatability of ±0.01–0.06 mm depending on the model. |
| Servo Motor | The electric motor inside each joint. It receives commands from the controller and moves the joint to the precise position requested. |
| TCP (Tool Center Point) | The point in space that the controller tracks during programmed motion. It’s usually defined as the tip or working point of whatever tool is attached. |
| Teach / Teaching | The process of manually guiding the robot to positions and recording them into a job. The programmer jogs the robot, then saves each position. |
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