Bent two-link SCARA places its vertical quill at the midpoint of a straight violet path.

What you need

Use a two-link simulator, a chosen start and end point and a consistent inverse-kinematics branch.

Distance traveled along the example line. 25 percent: 17.678 mm; 50 percent: 35.355 mm; 75 percent: 53.033 mm; 100 percent: 70.711 mm.
Distance traveled along the example line. Original Academy diagram using illustrative values; not a measured hardware result.
Read the diagram as a data table
Values used in the illustration
Condition or componentmm
25 percent17.678
50 percent35.355
75 percent53.033
100 percent70.711

The calculation

p(s) = (1 − s)p_start + s p_end, 0≤s≤1

p is an x-y position vector. A separate time law s(t) sets the speed; geometric interpolation alone does not define motion timing.

Worked example

Illustrative numbers. Replace them with your measured inputs.

From (100,100) to (150,50) mm, the midpoint is (125,75) mm and path length is √(50²+50²)=70.71 mm. Check every sampled point for reachability and joint-speed amplification, not only the two endpoints.

Try it step by step

  1. Sample the Cartesian segment and reject unreachable or colliding points with the full tool geometry included.
  2. Solve a continuous inverse-kinematics branch and inspect joint-angle plots for jumps.
  3. Apply a time law, calculate joint rates and accelerations, and increase duration or replan if any axis exceeds limits.
  4. Compare the simulated executed path with the intended line and document interpolation tolerances.

How to check the result

Measure maximum perpendicular deviation from the requested line across the complete path.

Common mistake to avoid

A collision-free line for the tool tip may still sweep an elbow through an obstacle. Endpoint-only checks miss this problem.

Reference reading

Primary references for the underlying models, APIs or application context. The worked numbers and plots above are educational calculations, not results reported by these sources.

Read our methods, limitations and safety notes.