Time-Optimal Trajectory Planning for Manipulation of Loosely-Placed Objects: the Waiter Motion

Source: H. Gattringer, A. Müller “Reliable Time-Optimal Point to Point Handling of Unmounted Objects with Industrial Robots”, ROMANSY 24 – Robot Design, Dynamics and Control, 2022.

Project Description

The project aims at solving the so-called general waiter problem. The waiter problem consists of moving a tray (which is attached to the robot end-effector), on which some cups are placed. The motion must be executed by the robot in the fastest way possible, from one pose to another, such that the cups do not slide at any time. The geometric path of the tray is prescribed, whereas its orientation represents a variable of the problem.


  • Sound knowledge of mechanics of machines
  • Sound knowledge of kinematics of robots
  • Strong initiative and attitude problem solving
  • Strong will to cope with demanding challenges
  • Keen on studying complex new theory

Not required but good to have:

  • Knowledge of optimization algorithms
  • Knowledge of Python programming
  • Knowledge of ROS

Target Objectives

  • Improved programming skills and ability to use third-party software (ROS)
  • Time-optimal trajectory planning of serial robots

Expected Results

  • Study of ROS and IRMA software
  • Planning of a time-optimal trajectory, satisfying the waiter constraints (no sliding of the cups)
  • Experimental tests

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