UR20 Teach Pendant Simulator

A browser-based UR20 robot teach pendant — program, preview, and export PolyScope X programs with zero installation.

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A fully client-side UR20 robot simulator that runs in any modern browser. No server, no install, no build step. Open one HTML file and you have a functional 6-DOF robot teach pendant with forward/inverse kinematics, 3D visualization, waypoint programming, and export to Universal Robots' native PolyScope X format.

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Features

Kinematics

• Full 6-DOF forward kinematics via standard DH convention (4×4 matrix chain)
• Numerical inverse kinematics using Levenberg-Marquardt with 200-iteration convergence, 0.1 mm tolerance
• Live IK on Cartesian XYZ slider drag — joint angles update in real time
• Singularity-safe: invalid IK targets are silently ignored, last valid state held

3D Visualization

• Hardware-accelerated WebGL via Three.js r158
• Schematic robot model: sphere joints + cylinder links, updates every frame
• PCFSoft shadow mapping, ACES filmic tone mapping
• Interactive OrbitControls: orbit, pan, zoom

Teach Pendant Interface

• 6 joint sliders (±360° range each)
• Cartesian XYZ sliders with live IK
• Quick-pose presets: Home, Zero, Up (smooth 500 ms animated transitions)
• Waypoint recording with 4 node types: moveJ, moveL, Wait/Sleep, Set I/O
• Waypoint list with inline delete and reorder controls
• Path playback: Play / Pause / Resume / Stop / Restart
• Undo / Redo — 60-state snapshot history (Ctrl+Z / Ctrl+Y)

Import / Export

• Import: .urpx (PolyScope X JSON), .script (URScript), .angles (ARTAB v2 Arduino), .csv (Arduino IK output)
• Export: .urpx (full PolyScope X v2 schema with safety block), .script (standalone URScript)

Persistence

• Auto-save to localStorage on every state change
• Session restored automatically on next open

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Quick Start

1. Download ur20_teach_pendant_v4.html
2. Open it in a browser (Chrome, Firefox, Edge, or Safari)
3. That's it

No Node.js. No Python. No server. No install.

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File Structure

File	Description
ur20_teach_pendant_v4.html	Complete simulator — the only file you need
README.md	This document
paper.md	Academic/technical paper describing the system

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Arduino CSV Pipeline

The simulator accepts CSV files output by Arduino sketches that compute inverse kinematics and log joint angles over serial.

CSV Format

# Lines starting with # are ignored (comments)
# Column order: J1, J2, J3, J4, J5, J6  (degrees, UR joint order base→wrist)
j1,j2,j3,j4,j5,j6
0.00,-90.00,0.00,-90.00,0.00,0.00
15.32,-85.10,12.44,-87.20,0.00,0.00
30.11,-79.55,24.88,-85.33,0.00,0.00

• Values are degrees, not radians
• Six columns per row, comma-separated
• Header row (j1,j2,...) is optional — non-numeric rows are skipped automatically
• Each row becomes one moveJ waypoint at default 50% speed / 50% acceleration

End-to-End Workflow

Arduino sketch
     │  computes IK, logs angles over Serial
     ▼
Serial monitor saves output as .csv
     │
     ▼
UR20 Simulator  ──  Import .csv  ──►  Waypoint list populated
     │
     ├──  Play  ──►  Preview trajectory in 3D
     │
     └──  Export .urpx  ──►  Load into PolyScope X or URSim

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Keyboard Shortcuts

Shortcut	Action
Ctrl+Z	Undo
Ctrl+Y	Redo
Space	Play / Pause path playback
Escape	Stop playback

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Export Formats

URPX (PolyScope X Native)

Exports a .urpx JSON file conforming to the PolyScope X v2 program schema. Includes:

• Full safety configuration block (required by PolyScope X loader — joint limits, tool speed/force limits, safety planes at UR20 factory defaults)
• Hierarchical node tree with ur-move-to, ur-wait, and ur-set-io nodes
• Motion profiles with speed, acceleration, and blend radius per node
• Embedded URScript mirror with t=N timed-move parameters
• Robot metadata and ISO 8601 creation timestamp

Validated against URSim 5.14. Programs load and execute without schema errors.

URScript (.script)

Exports a plain-text URScript program:

def program():
  movej([θ1,θ2,θ3,θ4,θ5,θ6], a=1.2, v=1.05, t=0)
  movel(p[x,y,z,0,0,0], a=1.2, v=0.25)
  sleep(1.5)
  set_digital_out(0, True)
end

Can be loaded directly into URSim's script editor or deployed to a real controller via the UR Dashboard Server load command.

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Technical Details

DH Parameters (UR20)

Joint	a (m)	d (m)	α (rad)
1	0.0000	0.2363	π/2
2	−0.8620	0.0000	0
3	−0.7287	0.0000	0
4	0.0000	0.2010	π/2
5	0.0000	0.1593	−π/2
6	0.0000	0.1543	0

Source: Universal Robots UR20 Technical Specification.

Inverse Kinematics Solver

Parameter	Value
Method	Levenberg-Marquardt (numerical)
Residual	Position-only (3 DOF)
Jacobian	Finite-difference, 3×6, δ = 1×10⁻⁶ rad
Max iterations	200
Convergence tolerance	0.1 mm
Linear solver	Gaussian elimination with partial pivoting
Damping λ init	1×10⁻³
Damping adaptation	×0.1 on improvement, ×10 on regression

Robot Specs

Property	Value
Model	Universal Robots UR20
DOF	6 (all revolute)
Reach	1750 mm
Payload	20 kg
Kinematics convention	Standard DH

Implementation

Property	Value
Language	Vanilla JavaScript ES2022
3D library	Three.js r158 (CDN via importmap)
External dependencies	None (beyond Three.js CDN)
Lines of code	~2750
Deployment	Single HTML file

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Browser Compatibility

Browser	Status
Chrome 90+	Supported
Firefox 89+	Supported
Edge 90+	Supported
Safari 15+	Supported
Mobile browsers	Functional (touch orbit supported via OrbitControls)

WebGL 2.0 required. Enabled by default in all listed browsers on hardware with GPU support.

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License

MIT License — see below.

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.