PAPAS
The increasing integration of mechanics, sensors and actuators into mechatronic systems and their control and regulation by software enables the development of new handling systems that are faster, more precise and more intuitive to programme. The prerequisite for this is an integrated system design process that includes modelling, simulation and optimisation and encompasses all sub-disciplines of mechatronics. The integrated design process makes it possible to build future handling systems on a modular basis and thus to integrate innovations from drive and peripheral manufacturers into systems more quickly and efficiently.
The aim of the PAPAS project is to make these design technologies accessible to machine and plant manufacturers and their component manufacturers and to realise modular, industrial-grade lightweight robots for the production of tomorrow based on a plug-and-play concept.
Runtime | 2003-05-01 till 2006-07-31 |
project partner |
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fields of application | industrial robotics |
funding |
Project Details
Today's industrial robots (as of 2006) are position-controlled handling devices that follow a predetermined path in space with great precision. This places high demands on the accuracy of the feeding and positioning of objects for many production tasks that are to be automated with the help of the robot. Some tasks, such as the joining of a bolt with a tight fit, can only be realised with great effort today with a robot that is exclusively position-controlled without the use of sensors.
Adjustable compliance
With its integrated sensor system, the LBR 3 lightweight robot is ideally suited for such tricky tasks. Each joint is equipped with a position sensor on the drive side and position and torque sensors on the output side. The robot can therefore be operated with position, speed and torque control. Trajectories are travelled precisely, highly dynamically and vibration-free; the compliance, i.e. a combination of position (orientation) and force (moment), can be specified at any point along the trajectory.
Compliant production assistant
By linking this new generation of robots with the industrial PC-based KUKA KR C robot controller, a completely new type of robot has been created: the RoboAssistant. It is designed so that humans and robots can share the workspace. In particular, the robot can react "sensitively" to touches across the entire arm. This ability can be utilised for a new, intuitive form of robot programming, programming by demonstration (PdV).
Image-supported and force-controlled joining
Fast and reliable assembly is achieved through a suitable combination of intelligent image processing, controlled compliance and an optimised robot path. Image processing provides an initial estimate of the global position of the parts to be joined. The force-torque sensors provide fast and high-resolution local information about the objects with which the robot is in contact.
In order to obtain a joining strategy that is as promising as possible, a trajectory is planned that is robust against positioning errors. For this purpose, optimisation is used to determine the trajectory for which the acceptable error of the initial estimate is maximum. Based on the geometric description of the parts to be joined obtained from the image processing, the controller parameters are determined automatically and integrated directly into the robot programming language KRL.
Focal points
To achieve the project objective, those involved in the project are working on the following focal points:
Communication
The communication system to be realised in PAPAS must fulfil many requirements from a wide range of application areas. At the protocol level, for example, services from the fieldbus sector, but also administrative and maintenance services must be realised.
The PAPAS protocol must provide synchronisation between the cyclically operating control system and the drives, sensors and mechatronic systems, which also operate cyclically. An interpolator cyclically calculates setpoints for each drive in the control system at constant, short intervals. Each drive follows the set values supplied cyclically by the interpolator by means of its own control system. This enables both precise control of individual drives and exact interpolation with any number of drives. The points in time at which the actual values are recorded and the points in time at which the set values become effective in the drive are just as important for the precise coordination of the drives as the accuracy of the interpolated set values and the measuring accuracy. A dimensional precision of 1 micrometre at a speed of 1 m/s, for example, corresponds to a time precision of 1 microsecond. The drives, sensors/actuators are typically adapted to different applications and control systems by parameterisation. In addition to the cyclical real-time data to be exchanged during operation, an acyclical but secure protocol is sufficient for the exchange of parameters and diagnostic information.
Design technologies for "plug-and-play"
The new plug-and-play drive and control technology opens up a new dimension of design freedom and a wealth of variants for the design of new handling systems, because new system architectures can be realised more easily using existing drive and control components. In particular, model-based control and regulation methods are indispensable for this, e.g. to improve machine dynamics, i.e. to perform a task faster, more accurately and with less vibration. Plug-and-play technology offers the potential to communicate dynamic parameters of participants on the bus to the control and regulation computers during registration.
Examples of this are
- Mass, centre of gravity and inertia sensor of a laser welding device or a gripper in relation to the connecting flange
- Maximum and nominal torque, as well as maximum speed of an electric motor
- Characteristics of a laser distance sensor or a force-torque sensor with regard to maximum measuring range and maximum measuring error
Corresponding control and regulation algorithms utilise this data to improve control and control quality. The traditional approach of defining such dynamic parameters via configuration files is more error-prone and requires significantly more effort each time the configuration is changed.
Flexible configurability with plug-and-play requires that the model-based control and regulation methods used can be easily adapted to the respective situation. In the PAPAS project, system models of machines are therefore set up in a component-orientated manner, as components such as gearboxes, motors and power modules can then be easily replaced in the model. Furthermore, optimisation-based design procedures are made available in order to fully exploit the additional design freedom of plug-and-play technology and to be able to control the system dynamics. The result of a design can be automatically loaded onto the control and regulation computers.
New robot systems, product innovations, applications
The first demonstrator based on the existing DLR lightweight arm, hereinafter referred to as "RoboWorker", is to be completed at an early stage of the project. It will be operated with the KUKA controller and controlled via a KUKA handheld programming device in order to provide (industrial) users with easy access to new technologies (lightweight construction, compliance, impedance control, torque control, kinematic redundancy). The familiar operating environment is retained. The coupling of the KUKA controller with the DLR lightweight robot will be based on a Cartesian interface, which will initially be implemented independently of the PAPAS protocol. This will make it possible to develop application scenarios for a compliant production robot with users and system partners alike at an early stage of the project. The applications can come, for example, from the field of human-robot interaction and from the field of production or assembly (e.g. joining operations).