SISCob

SISCob aims at developing a new intelligent and modular device mimicking the functions of biological articulations and their synergy for collaborative robots (cobots). This Safety Intelligent Sensor (SIS) device will connect the output shaft of an actuator to a robot link or to the end-effector when the actuator is in its terminal position; it will ensure the safe functioning of the robot itself and the safe interaction with the surrounding environment by providing the following services:

• an adaptive tunable compliant mechanical structure managing high frequency physical interactions;
• an online estimation of impedance models exploitable for predictive control;
• a real-time data transmission, allowing SISs to communicate as agents within an ad hoc body area sensor network that a central control unit can interrogate.

This project stems from the fact that manufacturing and manual services sectors rely on process improvements for reducing financial costs, raising quality and productivity. However, new societal and environmental constraints should also be accounted for: that is safety and environmental impact management and/or the lack of skilled manpower for specialized or arduous or hazardous work. To address these challenges, numerous R&D projects have focused on the cobots usage to collaborate with and assist human operators. However, safety issues have slowed down the introduction of robots working in close vicinity with humans. These barriers could be broken down with suitable technologies allowing for safe physical man/machine interaction without hindering the versatility and engineering possibilities of robots. In contrast to the state of the art of compliance based techniques for robot safety, our aim is to achieve this safety level independently of the robotic structure, actuation technologies and power along with the capability of robustly managing environmental uncertainties. These conditions are crucial for a real large-scale deployment on the market. We believe that the design of a very unique sensor could be the keystone of the solution. From a scientific point of view, two of the most critical identified issues are:

1. To propose a novel safety compliant articulated mechanism adapting its stiffness to impact forces on the robot links. This mechanism should be passive with the possibility to modulate actively its stiffness.
2. For a high quality robust control of the robot, the sensor should provide on-line a full model of the mechanical impedance the actuator’s shaft is interacting with. We will develop an innovative estimation approach, resilient to persistent excitation and consisting in two steps: a) Using an algebraic approach to select on-line the best candidate model from available data and b) Identifying the model’s parameters. Furthermore, a respiratory model could be combined with the impedance model to enhance its predictive capability for some specific applications.

Some advantages of the SIS include:

• Robot designers will have the possibility to conceive dependable and intrinsically safe robots with the SIS as a new low cost building block and without worrying about consequences on the actuators choice.
• The impedance model, estimated in real-time, will enable to supplement the safety functions by allowing the implementation of a fast predictive impedance control loop (reflex loop) of the actuators.
• When a robot is equipped with several SIS, the sensors network will permit to detect the impact/contact loci on the robot structure and trigger an appropriate global safety control strategy.
• Thanks to the delivered impedance model, the SIS will enable to use the efficient “model mediated teleoperation” technique in a new way for haptic teleoperation.

The « SIS » will be developed with a number of pre-industrial versions and tested on a modular robot for three applications covering three main robotics fields namely industrial robotics, medical robotics and assistive robotics.