Dominik Henrich

Development of the first force-controlled robot for otoneurosurgery.

Objective In some surgical specialties (eg, orthopedics), robots are already used in the operating room for bony milling work. Otological surgery and otoneurosurgery may also greatly benefit from the enhanced precision of robotics.

Space-efficient region filling in raster graphics

This paper presents fill algorithms for boundary-defined regions in raster graphics. The algorithms require only a constant-size working memory. The methods presented are based on the so-called “seed fill” algorithms that use the internal connectivity of the region with a given inner point. Basic methods, as well as additional hcuristics for speeding up the algorithm, are described and verified. Empirical results are used to compare the time complexities of the algorithms for different classes of regions.

Safe human-robot-cooperation: image-based collision detection for industrial robots

This paper analyzes the problem of sensor-based collision detection for an industrial robotic manipulator. A method to perform collision tests based on images taken from several stationary cameras in the work cell is presented. The collision test works entirely based on the images, and does not construct a representation of the Cartesian space. It is shown how to perform a collision test for all possible robot configurations using only a single set of images taken simultaneously.

Robot Manipulation of Deformable Objects

Besides the work in the field of manipulating rigid objects, currently, there are several research and development activities going on in the field of manipulating non-rigid or deformable objects. Several papers have been published on international conferences in this field from various projects and countries. But there has been no comprehensive work which provides both a representative overview of the state of the art and identifies the important aspects in this field. Thus, we collected these activities and invited the corresponding working groups to present an overview of their research. Altogether, nineteen authors coming from Japan, Germany, Italy, Greece, United Kingdom, and Australia contributed to this book. Their research work covers all the different aspects that occur when manipulating deformable objects. The contributions can be characterized and grouped by the following four aspects: * object modeling and simulation, * planning and control strategies, * collaborative systems, and * applications and industrial experiences. In the following, we give a short motivation and overview of the single chapters of the book. The simulation of deformable objects is one way to approach the problem of manipulating these objects by robots. Based on a physical model of the object and the occurring constraints, the resulting object shape is calculated. In Chapter 2, Hirai presents an energy-based approach, where the internal energy under the geometric constraints is minimized. Frugoli et al. introduce a force-based approach, where the forces between discrete particles are minimized meeting given constraints. Finally, Remde and Henrich extend the energy-based approach to plastic deformation and give a solution of the inverse simulation problem. Even if the object behavior is predicted by simulation, there is still the question of how to control the robot during a single manipulation operation. An additional question is how to retrieve an overall plan for the concatenated manipulation operations. In Chapter 3, Wada investigates the control problems when positioning multiple points of a planar deformable object. McCarrager proposes a control scheme exploiting the flexibility, rather than minimizing it. Abegg et al. use a simple contact state model to describe typical assembly tasks and to derive robust manipulation primitives. Finally, Ono presents an automatic sewing system and suggests a strategy for unfolding fabric. In several manipulation tasks, it is reasonable to apply more than one robot. Especially in cases, where the deformable object has to take a specific shape. Since the robots working at the same object are influencing each other, different control algorithms have to be introduced. In Chapter 4, Yoshida and Kosuge investigates this problem for the task of bending a sheet of metal and exploits the relation ship between the static object deformation and the bending moments. Tanner and Kyriakopoulos regard the deformable object as underactuated mechanical system and make use of the existence of non-holonomic constraints. Both approaches model the deformable object as finite elements. All of the above aspects have their counterpart in different applications and industrial experiences. In Chapter 5, Rizzi et al. present test cases and applications of their approach to simulate the manipulation of fabric, wires, cables, and soft bags. Buckingham and Graham give an overview of two European projects processing white fish including locating, gripping, and deheading the fish. Maruyama outlines the three development phases of a robot system for performing outage-free maintenance of live-line power supply in Japan. Finally, Kamper presents the development of a flexible automatic cabling unit for the wiring of long-tube lighting with plug components.

Fast Motion Planning by Parallel Processing – a Review

One of the many features needed to support the activities of autonomoussystems is the ability to plan motion. This enables robots to move in theirenvironment securely and to accomplish given tasks. Unfortunately, thecontrol loop comprising sensing, planning, and acting has not yet beenclosed for robots in dynamic environments. One reason involves the longexecution times of the motion planning component. A solution for thisproblem is offered by the use of highly parallel computation. Thus, animportant task is the parallelization of existing motion planning algorithmsfor robots so that they are suitable for highly parallel computation. Inseveral cases, completely new algorithms have to be designed, so that aparallelization is feasible. In this survey, we review recent approaches tomotion planning using parallel computation. As a classification scheme, weuse the structure given by the different approaches to the robot’smotion planning. For each approach, the available parallel processingmethods are discussed. Each approach is assigned a unique class. Finally,for each research work referenced, a list of keywords is given.

Point-to-Point trajectory planning of flexible redundant robot manipulators using genetic algorithms

The paper focuses on the problem of point-to-point trajectory planning for flexible redundant robot manipulators (FRM) in joint space. Compared with irredundant flexible manipulators, a FRM possesses additional possibilities during point-to-point trajectory planning due to its kinematics redundancy. A trajectory planning method to minimize vibration and/or executing time of a point-to-point motion is presented for FRMs based on Genetic Algorithms (GAs). Kinematics redundancy is integrated into the presented method as planning variables. Quadrinomial and quintic polynomial are used to describe the segments that connect the initial, intermediate, and final points in joint space. The trajectory planning of FRM is formulated as a problem of optimization with constraints. A planar FRM with three flexible links is used in simulation. Case studies show that the method is applicable.

3D Collision Detection for Industrial Robots and Unknown Obstacles using Multiple Depth Images

In current industrial applications without sensor surveillance, the robot workcell needs to be rather static. If the environment of the robot changes in an unplanned manner, e. g. a human enters the workcell and crosses the trajectory, a collision could result. Current research aims at relaxing the separation of robot and human workspaces. We present the first approach that uses multiple 3D depth images for fast collision detection of multiple unknown objects. The depth sensors are placed around the workcell to observe a common surveilled 3D space. The acquired depth images are used to calculate a conservative approximation of all detected obstacles within the surveilled space. Using a robot model and a segment of its future trajectory, these configurations can be checked for collisions with all detected obstacles. If no collision is detected, the minimum distance to any obstacle may be used to limit the maximum velocity. The approach is applicable to a variety of other applications, such as surveillance of tool engines or museum displays.

Velocity control for safe robot guidance based on fused vision and force/torque data

We present a method for securing guided robot motions in terms of human/robot cooperation. For this, we limit the maximum allowable velocity of the robot based on the distance to the human or to the next obstacle and generate the effective velocity using guidance informations provided by the interacting human. Therefore, we fuse the two heterogenous data types of a camera and a force torque sensor. The cameras are used to monitor the robots workspace applying a difference image method. Given this obstacle information, distances are calculated between the robot and humans or objects in the environment respectively. The distance within each image is determined via an extended difference image method. The distances acquired from each camera are fused to approximate the real robot to object distance within the workspace. This distance regulates the maximum allowable velocity of the robot. The force/torque sensor provides the guidance information, i.e. amount, direction of the force and moment. This information is used to generate the robots movement taking the maximum allowable velocity into consideration

Manipulating deformable linear objects - contact states and point contacts

The task of handling non-rigid one-dimensional objects by a robot manipulation system is investigated. To distinguish between different non-rigid object behaviors, five classes of deformable objects from a robotic point of view are proposed. Additionally, an enumeration of all possible contact states of one-dimensional objects with polyhedral obstacles is provided. Finally, the qualitative motion behavior of linear objects is analyzed for stable point contacts. Experiments with different materials validate the analytical results.

Human-robot cooperation: safe pick-and-place operations

We present an industrial robot system whose workspace is supervised by several stationary cameras to ensure safe human-robot cooperations. All robot transfer motions are checked for collision by detecting obstacles using a difference image method. Whenever a collision is detected, the robot motion path is changed accordingly. The presented algorithm enables robots to perform safe pick-and-place operations exhibiting real time behaviour through efficient image processing.