MotionGen

MotionGen is a browser-based planar mechanism design and kinematic synthesis platform developed by Mechanismic Inc. and Stony Brook University. It enables engineers, students, and researchers to synthesize, simulate, and visualize planar linkage mechanisms directly in a web browser without installing software.

Unlike traditional mechanism design workflows where engineers manually apply Burmester theory or iterate through linkage geometries by hand, MotionGen uses a unified computational synthesis approach. Users define prescribed positions, fixed pivot constraints, or target coupler curves, and the platform computes viable linkage solutions automatically.

The platform combines exact kinematic synthesis with machine learning path synthesis, covering both cases where a small number of precision positions are defined and cases where an arbitrary target coupler curve needs an approximate four-bar solution. This dual approach addresses the full range of practical mechanism design problems that arise in academic and industry settings.

MotionGen also supports full N-bar mechanism simulation, allowing engineers to model planar linkages with any number of links, revolute and prismatic joints, and multiple degrees of freedom. Kinematic graphs, coupler curve visualization, and real-time animation provide quantitative and visual feedback during the design process.

Because of its accessible browser-based format and direct connection to the SnappyXO physical hardware kit ecosystem, MotionGen has found strong adoption in undergraduate engineering education as well as in robotics, automation, and prosthetics design.

Key Features

• Kinematic synthesis for planar four-bar linkages using the unified Burmester algorithm for simultaneous type and dimensional synthesis from up to five prescribed coupler positions
• Fixed-pivot and moving-pivot geometric constraints in synthesis for structurally grounded design requirements
• N-bar mechanism simulation for planar linkages with any number of links, revolute and prismatic joints, and one or more degrees of freedom
• Machine learning path synthesis using variational autoencoder models to generate defect-free approximate four-bar solutions for arbitrary target coupler curves
• Mobility analysis with automated degree-of-freedom computation for planar mechanisms with mixed joint types via extended pebble game algorithm
• Real-time coupler curve generation and visualization during mechanism animation
• 2D and 3D visualization modes for mechanism models
• Custom shape drawing and attachment to mechanism links for scene context and assembly representation
• Export of part geometries for 3D printing and laser cutting
• Integration with SnappyXO hardware kits for physical mechanism prototyping
• Controlled actuation module for driven mechanism simulation
• Kinematic graphs for quantitative analysis of joint positions, velocities, and accelerations
• Web-based with no installation required; mobile app available for four-bar mechanism work on iOS and Android

Best For

Mechanical engineering students and educators covering mechanism design and kinematic synthesis in undergraduate curricula, practicing mechanical engineers who need to quickly synthesize linkage geometries that guide a component through prescribed positions without setting up formal optimization problems, and robotics and automation engineers designing walking robots, drawing bots, grippers, and other linkage-driven mechanisms who want to move from motion requirements to viable linkage geometry interactively.

The SnappyXO integration makes it particularly suited to hands-on education contexts where software design connects directly to physical prototyping.

Who It's Not For

Engineers who need full three-dimensional multibody dynamics simulation with flexible bodies, contact mechanics, control system co-simulation, and load extraction for downstream structural analysis. MotionGen is a planar kinematic tool. It handles two-dimensional mechanism geometry, position analysis, and synthesis, but does not compute forces, stresses, or dynamic loads through the mechanism. Those requirements are served by tools such as Altair MotionSolve, MSC Adams, or Simpack.

Engineers working with spatial three-dimensional mechanisms also fall outside MotionGen's current planar scope.

Platform

Browser-based web application at motiongen.io, accessible without installation in Chrome, Edge, and Firefox. Free registration required for full access.

Mobile app for iOS and Android covers four-bar mechanism simulation only. The web version provides the full feature set including N-bar simulation and machine learning path synthesis.

The platform is developed and maintained at Stony Brook University and Mechanismic Inc., with documentation available at docs.motiongen.io and academic support through Dr. Purwar's research group.

Pricing

Free to use with account registration. The web application and its full feature set are available without charge.

SnappyXO hardware kits are available for purchase separately through snappyxo.com for physical prototyping. Academic institutions and instructors can incorporate MotionGen into course curricula without licensing cost. Mechanismic Inc. offers contact options for institutional and commercial inquiries.

Pros

• Kinematic synthesis, computing what linkage is needed rather than just simulating an existing one, is rare among accessible web tools and directly addresses the hardest part of mechanism design
• Unified synthesis algorithm computes all viable four-bar linkage types and dimensions simultaneously from posed constraints, removing the need to solve Burmester equations manually
• Machine learning path synthesis generates defect-free approximate solutions for target coupler curves that exceed the exact synthesis limit of five positions
• Free browser-based access with no installation lowers the adoption barrier for students and educators significantly
• Connection to SnappyXO physical hardware closes the loop from computational synthesis to physical prototype within the same design environment
• Backed by peer-reviewed kinematics research from Stony Brook University, with synthesis algorithms that are academically validated rather than heuristic approximations

Cons

• Limited to planar mechanisms with no spatial or three-dimensional mechanism synthesis or simulation capability
• No force, torque, or dynamic load calculation; analysis is purely kinematic rather than kinetic
• No integration with CAD systems for geometry import or export to downstream mechanical design workflows
• Machine learning path synthesis quality depends on training data coverage and may produce lower-accuracy results for unusual target curves
• The academic development context means release cadence, long-term commercial support, and enterprise reliability commitments are less defined than for commercial tools
• Mobile app is restricted to four-bar mechanisms; full N-bar simulation requires the web version

Rating

⭐ 4.2 / 5

Editorial Take

MotionGen occupies a genuinely useful and underserved position in the mechanism design tool landscape. Kinematic synthesis capability at this level of accessibility, backed by peer-reviewed algorithms and available free in a browser, has no direct equivalent among mainstream engineering tools. For educators and engineers working with planar linkages, it removes the most technically demanding part of mechanism design and replaces it with an interactive, computationally grounded workflow.

Alternatives

SAM Mechanism Designer, Linkage (Dave Bacher), Working Model 2D, ADAMS/View, KISSsoft, GIM (University of the Basque Country)

Used In

• Undergraduate mechanism design coursework
• Robotics leg and walking mechanism development
• Automotive suspension and linkage conceptual design
• Prosthetics and assistive device mechanism design
• Industrial gripper and pick-and-place mechanism synthesis
• STEM education from middle school through undergraduate engineering
• SnappyXO robot kit mechanism design and prototyping

Founded

2010 (initial iOS app; web platform expanded thereafter by Mechanismic Inc. and Stony Brook University)