Mobile manipulator
A robot system composed of a self-propelled base and a robot arm is generally referred to as a mobile manipulator . They are often referred to by the much more general term service robot , especially in research and for non-industrial applications . In the case of industrial applications, on the other hand, people usually speak of mobile manipulators or mobile robots (poor).
Components
Mobile robot platform
Both classic driverless transport systems and mobile robots can be used as a mobile basis . The use of a mobile robot has the advantage that it can navigate freely and autonomously in space and thus the manipulator in case of problems (target object out of range, manipulation from the current position kinematically not possible, change in the position of the parts to be processed, etc.) can provide immediate support instead of just transporting it to a fixed position. The maneuverability of the platform is of great importance. In contrast to AGVs, a mobile robot can also move to dynamically assigned positions at any time. However, the classic differential kinematics reaches its limits, especially in the immediate vicinity of workstations, and moving the robot is then only possible through more or less complex maneuvering. The use of omnidirectional drives is therefore becoming more and more popular.
Storage options
If the mobile manipulator is to transport objects efficiently, it must be equipped with suitable storage facilities. With the appropriate design, these can also be used to enable the handle to be changed without using a second arm. (For example, a beer bottle that has been pulled out of the case by the cap must first be set down and grasped by the body before it can be poured.) Larger storage options make the robot's work more efficient in principle, but also make it more difficult to navigate the vehicle.
Manipulator arm
This can be an industrial robot as well as a specially developed robotic arm. Since a selection of small and light robotic arms is now commercially available, the use of arms developed in-house has decreased significantly. (See also: Flexible manipulator arm )
Gripper
The end effector must be selected appropriately for the item to be manipulated. Anthropomorphic grippers with multiple moveable fingers are increasingly available and are mainly used in research.
Image processing
If the robot is to manipulate parts in the work environment, an image processing system is almost always required. If only firmly learned arm movements are to be carried out, at least the offset between the current platform position and the platform position used during the learning process must be determined and taken into account. In order to take on the tasks of human workers, the robot also has to cope with more or less disordered parts (also known as box handles) or variable storage locations.
Coordinating control
The individual controls of mobile robots and robot arms have been in use for decades and are well developed. When combining both systems, however, a very large number of possible error and problem cases arise, which makes it necessary to add an additional coordinating control. Above all, this should independently find solutions if the manipulation ordered cannot be carried out, but would be possible from a different pose. The control of the entire system as a closed kinematic chain is helpful , but this is extremely difficult to implement due to the high redundancy.
security system
In principle, it is possible to use the safety devices that are used for stationary manipulator arms or normal autonomous vehicles for mobile manipulators as well. However, if a mobile manipulator shares the work area with people or at least other vehicles, completely new and very high demands are made on the security system, since a great many possible dangerous situations arise.
Advantages and disadvantages
When combining mobile robotic platforms with robotic arms, the resulting advantages and disadvantages are greater than the sum of their respective parts.
Advantages:
- The range of functions and possible applications increase by leaps and bounds.
- The entire robot system becomes considerably less dependent on supporting systems (loading and unloading stations, conveyor technology, transfer devices, ...) and can thus, at least in theory, be cheaper.
- Mobile manipulators also make it possible to automate more complex physical activities that could previously only be carried out by humans and often lead to health problems for them due to the physical strain.
- The overall system can react much more flexibly to inaccuracies and deviations, for example by tracking the base of the arm if an object cannot be reached directly.
Disadvantage:
- Due to the requirements of both components, they often hinder each other:
- The arm needs a large stable base to work efficiently, but the platform should be small and light in order to navigate efficiently.
- The shorter the cycle times of the platform, the faster it has to travel and the less precisely target positions are reached. However, the less precisely the start position of the arm is known, the longer its cycle times will be due to the necessary corrections.
- In order to increase the running time of a battery-operated platform, the total weight and power consumption should be minimized. However, the more functions (and therefore mostly additional components) it combines, the more efficiently a robot arm works.
- Due to the fact that the working environment of the arm is constantly changing, many previously used auxiliary structures (parts feed with a defined end position relative to the arm, unchangeable transfer positions for components, defined lighting, etc.) can no longer be used or only with great difficulty.
- In addition, many mobile manipulators are not flexible enough to be used for quickly changing tasks. This is one of the greatest inhibitions for widespread use, even in small and medium-sized businesses.
- When interacting with people, completely new dangerous situations arise that place increased demands on the safety technology and severely limit the proportion of enforceable solutions compared to the solutions that are already technically feasible.
- There are currently no fully applicable standards, guidelines or design proposals for this type of robot, making the possible legal consequences of injury or damage difficult to predict.
- With the increased number of options for action, there are also disproportionately higher demands on the control of the overall system, in particular with regard to the autonomous error handling. This also increases the risk of machine downtime.
Areas of application
The possible areas of application for mobile manipulators are diverse and not fully foreseeable at the moment. Some popular uses are:
Collection and delivery services in the household
Led by the widespread application of fetching beer, especially in research projects in the field of service robotics, tasks for demonstration purposes are used which also occur in private households and are accordingly media-effective. The scientific challenge in these tasks is usually considerably greater than the expected economic benefit.
maintenance
As the proportion of elderly people and people in need of care increases, so will the need for care workers. It is expected that by 2050 the proportion of people in need of care will triple in relation to the number of people in employment. Therefore, in various research projects, especially in Japan, intensive work is being carried out on care robots.
Picking
Development projects are currently underway to use mobile manipulators for picking heavy or unwieldy components. There, mistakes that can cause high follow-up costs are to be prevented. In addition, human workers are freed from tasks that are harmful to their health in the long term, which becomes all the more relevant the further the average age of the workforce increases.
Milestones
| year | Project / product | Company / institution | country |
|---|---|---|---|
| 1996 | Hilare 2bis | LAAS-CNRS |
 France
|
| 2000 | Jaume | Jaume University, Robotic Intelligence Lab |
 Spain
|
| 2004 | Fausto | University of Verona |
 Italy
|
| 2005 | ASSISTOR | BMBF research project |
 Germany
|
| 2006 | MM-500 SK | Neobotix GmbH |
Germany
|
| 2008 | PR2 | Willow garage |
 United States
|
| 2008 | MM-800 | Neobotix GmbH |
Germany
|
| 2009 | Little helper | Aalborg University |
 Denmark
|
| 2010 | Omnirob | KUKA robots |
Germany
|
| 2010 | KUKA youBot | KUKA labs |
Germany
|
Manufacturer
The main manufacturers of commercial mobile manipulators are:
-
Germany:
- Artur Bär Maschinenbau GmbH
- KUKA
- Neobotix GmbH
-
United States
Web links
Manufacturer:
Research projects and institutes:
- HAW Ingolstadt: Mobile robotics in pre-order picking
- BMBF project ASSISTOR
- Aalborg University: Little Helper project
- Fraunhofer IPA: rob @ work project
Individual evidence
- ↑ Martin Hägele, Nikolaus Blümlein, Oliver Kleine et al .: EFFIROB - Profitability Analysis of New Kinds of Service Robotics Applications and Their Significance for Robotics Development , Fraunhofer IPA & ISI, 2011, p. 11
- ↑ Willow Garage application Beer-Me-Robot. Retrieved August 5, 2011 .
- ^ R. Schnabel: Future of care - press release. University of Duisburg-Essen and ZEW, May 2, 2007