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is an obvious but problematic solution, at least from an industrial application point of view, due to the high cost of this device. Another solution that can be envisaged concerns the development of a hybrid impedance/force controller to independently control the free and constrained directions of motion during the contact | is an obvious but problematic solution, at least from an industrial application point of view, due to the high cost of this device. Another solution that can be envisaged concerns the development of a hybrid impedance/force controller to independently control the free and constrained directions of motion during the contact | ||
phase. | phase. | ||
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| + | === An inspection system to characterise burrs === | ||
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| + | === Autonomously learning the deburring skill === | ||
== QUADRIVIO == | == QUADRIVIO == | ||
Revision as of 17:04, 24 December 2012
Contents
FIDELIO: FIxtureless DEburring of wheeLs by human demonstratIOn
Modern industrial robots are complex and powerful machines, able to execute a wide range of different tasks with high speed and accuracy. Nevertheless, they still have a low degree of autonomy and adaptability, and need a human operator to learn new tasks or tune existing ones.
In the last twenty years robotic researchers have been focusing on the Learning From Observation paradigm, developing prototypic robotic systems able to observe and learn from human operations. In this new paradigm, the information coming from a range of observations is analysed and transformed into an abstract representation of the task. By using such information, and exploiting the abstraction capabilities of a suitable cognitive system, the robot is able to autonomously generate a program to reproduce the task, even if the environment is different from the one observed during the learning phase.
The FIDELIO project aims at researching into the feasibility (and the related advantages) of this innovative approach in an industrial application scenario, exemplified by a fixtureless wheel deburring task. To this end, a robotised cell has be set up, composed of a Comau SmartSix industrial manipulator and a workstation where aluminium wheels are placed for deburring. On top of the workstation a camera frames the workspace in order to locate the wheel. The arm is equipped with a pneumatic deburring tool connected to the robot end-effector through a force/torque sensor. In addition, an eye-in-hand camera is mounted at the robot end-effector, framing the cutting tool and the deburring edge.
The experiment focused on three main topics: an innovative programming technique based on walk-through programming, an eye-in-hand inspection system to measure burrs characteristics, and a methodology to autonomously learn the deburring skill.
Walk-through programming
In the walk-through programming the human operator plays the role of a teacher that physically walks the robot through the desired path. Furthermore, in an industrial application, like metal finishing or spray painting, the physical interaction between the human operator and the robot should be conceived in such a way that the teacher has the impression to grab a real tool, e.g. a deburring tool or a spray gun, instead of the robot end-effector.
The role of the control system is thus to accommodate for the motion commanded by the teacher, mimicking the same dynamic behaviour of the real tool, i.e. behaving like a virtual tool that exhibits the same mechanical properties of the real tool. At the same time, the admittance controller allows to introduce two active safety tools that contribute to make human-robot interaction, during the programming operation, safe. On one hand, an adaptive nonlinear viscuous friction limits the maximum end-effector velocity. On the other hand, virtual fences create a separation between the human body and the robot work-space.
The walk-through programming has been implemented and tested on a Comau SmartSix industrial manipulator, equipped with an ATI 6-axis wrist force torque sensor, exploiting the open version of the COMAU C4G controller.
The tests revealed that one of the most challenging problem in walk-through programming is the execution of a motion keeping the tool in contact with an hard surface. In fact, when the operator grabs the tool his/her forces and moments are transmitted to the sensor, allowing him/her to walk the robot through the desired path. If the operator, however, brings the tool into contact with a hard surface, two phenomena can be observed. First, the transition between free motion and contact is characterised by impulsive forces that are obviously opposing the robot motion. Then, if a stable contact can be established, the sensor measures the combination of the operator and the contact surface reaction forces. As a consequence, using a single sensor, wherever it is mounted, allows to measure only the superposition of the operator and the contact forces, giving the control system an information that does not allow to react independently to each of them. Using two force/torque sensors is an obvious but problematic solution, at least from an industrial application point of view, due to the high cost of this device. Another solution that can be envisaged concerns the development of a hybrid impedance/force controller to independently control the free and constrained directions of motion during the contact phase.
An inspection system to characterise burrs
Autonomously learning the deburring skill
QUADRIVIO
The popularity of the research on unmanned ground vehicles has been recently increasing due to their usefulness in different operating environments. Planetary explorations, search and rescue missions in hazardous areas, surveillance, humanitarian demining, as well as agriculture applications such as pruning vine and fruit trees, are examples of potential applications of autonomous vehicles in natural environments. Unlike indoor mobile robotics, where only flat terrains are considered, outdoor robotics deals with all possible natural terrains. The unstructured environment and the terrain roughness including moving obstacles and poorly traversable terrains make the problem extremely challenging. All-Terrain Vehicles (ATVs) are suitable to drive in outdoor environments and through poorly traversable terrains, and compared to other movile platforms can rive at higher speed. ATVs, however, are also characterised by poor stability, roll- and tip-over phenomena, and excessive side slip. Those being the main drawbacks of these vehicles. The QUADRIVIO project aims at developing a low-cost unmanned ground vehicle for search and rescue missions in hazardous areas, possibly after a natural disaster. To achieve this challenging goal the project develops:
- a virtual rider, a low-level stabilisation system, including roll/tip-over prevention and obstacle avoidance mechanisms, that makes the vehicle autonomous at least for short range navigation
- a path planner that finds the best path in presence of rough an sloping terrains, taking into account the vehicle kinematic and dynamic constraints
- an ATV tracking controller that, acting on steer, throttle and brakes, tracks the desired path, ensuring the vehicle stability
A further aim of the QUADRIVIO project is the development of an airdrop system to parachute the vehicle on the operating area when, due to a natural disaster, all the main roads have been seriously damaged.