Robotics & Hardware · 2023 · prototype
SCARA Pick-and-Place Robot
Selective Compliance Articulated Robot Arm for precision planar sorting and payload transfer.
01 / Overview
A SCARA (Selective Compliance Assembly Robot Arm) configuration engineered for rapid, planar pick-and-place operations. Features two parallel rotary joints providing compliance in the horizontal XY plane while maintaining high rigidity along the vertical Z-axis.
02 / Problem
Industrial pick-and-place applications require high repeatability in horizontal transfers with rigid vertical positioning, requiring accurate inverse kinematics calculations on constrained microcontrollers.
03 / Contribution
Derived the 2-link planar inverse kinematics equations, designed joint linkage geometries, and programmed stepper/servo position trajectories.
04 / System architecture
Physical + hardware
- Two-link planar arm with precision bearings and low-backlash timing belt reductions
- NEMA stepper motors with microstepping drivers for high angular resolution
- End-effector miniature vacuum suction cup and micro-servo mechanical gripper
- Optocoupled homing limit switches for zero-datum calibration
Firmware + software
- Analytical 2D inverse kinematics solver translating target cartesian (X, Y, Z) coordinates to joint angles (theta 1, theta 2)
- Trapezoidal acceleration profiling for smooth start/stop motion without payload dislodgement
- Coordinate boundary enforcement to prevent arm singularity lockups
Signal flowMicrostepping driver array connected to dedicated hardware step/dir pulse pins, with optically isolated endstop sensor inputs.
05 / Engineering decisions
- 01Selected SCARA topology over 6-axis articulated arm to maximize horizontal speed, structural rigidity, and payload capacity per cost.
- 02Employed timing belt linkages to locate heavy motor masses at the base, minimizing arm inertia.
06 / Results + constraints
Observed results
- Achieved repeatable XY positioning within ~1.5mm tolerance on test bed.
- Successfully automated sorting cycles between two designated coordinate trays.
Current limitations
- Working envelope limited to semicircular planar radius of arm lengths.
- Manual calibration required upon initial power-on prior to homing cycle.