Jido

Path Planner for Manipulation in Human Presence : MHP module

Manipulation in the presence of humans is also an important aspect when humans and robots need to interact closely to exchange or manipulate objects. Not only must the robot's motion be calculated, by taking into account the human's dynamics and kinematics, but also the robot's own placement must take into account both the human's comfort and the current task.

Our approach is based on separating the whole problem of manipulation, e.g a robot giving an object to the human, into 3 stages.

Each of these stages will produce the corresponding result and past it to the next stage:

- Spatial coordinates of the point where the object will be handled to the human,

- The path that the object will follow from its resting position to human hand as it was a free flying object,

- The path of the whole body of the robot along with its posture for manipulation.

All these items must be calculated by taking explicitly into account the human partner to maintain his safety and his comfort. Not only the kinematic structure of the human, but also his vision field, his accessibility, his preferences and his state must be reasoned in the planning loop in order to have a safe and comfortable interaction. In each steps of the items stated above, the planner ensures humans safety by avoiding any possible collision between the robot and the human.

1- Calculating object position

One of the key points in the manipulation planning is to decide where robot, human and the object meet. In classical motion planners, this decision is made implicitly by only reasoning about robot's and the object's structure. The absence of human is compensated by letting him adapt himself to the robot's motion, thus making the duty of the human more important and the motions of the robot less predictable. We present 3 properties of the interaction, safety, visibility and arm comfort, that will help us to find safe and comfortable coordinates of the object where the robot will handle it to the human. These properties are represented as 3D grids and most suitable (lower cost) point in this grid is assigned to be the point where the robot will place the object for the human to handle.

2- Calculating object path

As we found where the robot must place the object in the previous stage, we now have to find the path that the object will take from its initial position to this final position. To find this path we use a 3D grid based approach which we build around the human.

This grid contains a set of cells with various costs derived from the relative configuration of the human, his state, his capabilities and preferences. A minimum-cost path search from object's current position to the previously found object exchange position is performed and this path is assigned to be the object's path.

3- Calculating robot path

Eventhough we found a path for the object (and robot's hand) to follow, it is not enough to produce a acceptable robot motion in HRI context where the motion should be safe, comfortable and predictable. With this motion the robot must make clear of its intention.

The third and final stage of planning consists of finding a path for the robot that will follow object's motion. The object's motion is computed as it was a freeflying object. But in reality it is the robot who holds the object and who will make the object follow it's path.

To adapt the robot structure to the object's motion, we use Generalized Inverse Kinematics algorithm with two tasks.

MHP video 1

MHP video 2

related publications

Supervision and Motion Planning for a Mobile Manipulator Interacting with Humans

Sisbot, E. Akin; Clodic, Aurélie; Alami, Rachid; Ransan, Maxime 3rd ACM/IEEE International Conference on Human-Robot Interaction (HRI 2008)

Human Robot collaborative task achievement requires adap- ted tools and algorithms for both decision making and mo- tion computation. The human presence as well as its be- havior must be considered and actively monitored at the decisional level for the robot to produce synchronized and adapted behavior. Additionally, having a human within the robot range of action introduces security constraints as well as comfort considerations which must be taken into ac- count at the motion planning and control level. This pa- per presents a robotic architecture adapted to human robot interaction and focuses on two tools: a human aware ma- nipulation planner and a supervision system dedicated to collaborative task achievement.

full pdf file


Arm Control

A soft-motion trajectory planner was developed with the objective of ensuring safety and comfort to humans interacting with the manipulator. The objective of this planner is to facilitate the hybrid force-vision control of the manipulator. A direct illustration of the capabilities of this motion trajectory planner is given by the transport of a cup of tea or a glass of water. It is used daily to animate the manipulator robot Jido.

related publications

On-line trajectory planning of robot manipulator's end effector in Cartesian Space using quaternions I. Herrera and D. Sidobre 15th Int. Symposium on Measurement and Control in Robotics