The difference between trajectory planning and path planning

Trajectory planning and path planning are two important concepts in robot motion planning, and they have the following differences:

Different definitions: trajectory refers to the actual path that the robot passes through in the process of movement, while path refers to the planned path of the robot movement, which is an abstract line segment.

Different goals: the goal of trajectory planning is to generate the path that the robot can actually move, so as to keep the robot stable, accurate and efficient during the movement. The goal of path planning is to generate the optimal path of robot movement, so that the robot can reach the end point in the shortest distance or time between the given starting point and the end point.

Different implementation methods: trajectory planning is usually carried out in the joint space or Cartesian space of the robot, and the trajectory of the robot is generated by planning the joints or postures of the robot. Path planning is usually carried out in the free space of the robot, and the path of the robot is generated by search algorithm or optimization algorithm.

Different algorithms: Trajectory planning usually adopts speed planning algorithm or acceleration planning algorithm to generate smooth and continuous robot trajectory. Path planning usually uses search algorithm such as A* algorithm or RRT algorithm, or optimization algorithm such as least square method or nonlinear programming to generate the optimal path of robot.

To sum up, trajectory planning and path planning have obvious differences in definition, objectives, implementation methods and algorithms, but they are both indispensable parts of robot motion planning, which can provide important support and guarantee for robot motion control.