Marie Jonsson

On force control for assembly and deburring of castings

Traditional industrial robots have problems interacting with an uncalibrated, ill-defined environment where part geometry and position may vary. Active force control technology has therefore been suggested as a solution to add the extra sensory dimension needed to handle manufacturing tasks like assembly and deburring. The technology is proposed to give increased flexibility compared to other solutions and force control systems are available commercially. Active force control installations, however, are still uncommon in industry. This paper presents two cases of force control applications; assembly of a compliant carbon fiber structure and deburring/cleaning of iron castings. Based on these two cases, some issues are raised concerning how the technology can be further developed to fit the industrial setting, and the proposed benefits are re-examined and refined. The two cases show that programming, parameter setting and ease of use are critical components in lowering the industrial threshold, together with increased possibilities for application-specific compensation and filtering. Force control does, however, show great potential in extending the boundaries for variance in product and equipment like grippers and fixtures as well as decreasing the need for calibration of for example virtual models used for programming compared to traditional automated solutions.

Force controlled assembly of flexible aircraft structure

The use of industrial robots in the aircraft industry has been hampered by a combination of poor accuracy of the robots and poor calibration of the workcell, and also manufacturing variability in composite parts. A way to handle these difficulties is using force control. An experimental case where a semi-compliant rib is aligned to multiple surfaces is used as an example to show this. The constraint-based task specification framework is used for the modelling and control, and the search and alignment sequence required for the assembly is modeled with a state machine. An implementation on an industrial robot system is presented and experimental data is evaluated. The described approach is easy to apply to other fields and more complicated assembly operations as well.

Force Controlled Assembly of a Compliant Rib

Automation in aerospace industry is often in the form of dedicated solutions and focused on processes like drilling, riveting etc. The common industrial robot has due to limitations in positional a ...

Force Feedback for Assembly of Aircraft Structures

Variability in composite manufacture and the limitations in positional accuracy of common industrial robots have hampered automation of assembly tasks within aircraft manufacturing. One way to handle geometry variations and robot compliancy is to use force control. Force control technology utilizes a sensor mounted on the robot to feedback force data to the controller system so instead of being position driven, i.e. programmed to achieve a certain position with the tool, the robot can be programmed to achieve a certain force. This paper presents an experimental case where a compliant rib is aligned to multiple surfaces using force feedback and an industrial robot system from ABB. Two types of ribs where used, one full size carbon fiber rib, and one smaller metal replica for evaluation purposes. The alignment sequence consisted of several iterative steps and a search procedure was implemented within the robot control system. The technology has the potential to lessen the need for dedicated tooling, reduce the need for traditional workspace calibration and can be used in several other applications, such as pin and socket type assemblies found in pylons or landing gear or “part to part” assemblies such as leading edge ribs to spar.