Dynamic Identification of the Franka Emika Panda Robot With Retrieval of Feasible Parameters Using Penalty-Based Optimization

In this letter, we address the problem of extracting a feasible set of dynamic parameters characterizing the dynamics of a robot manipulator. We start by identifying through an ordinary least squares approach the dynamic coefficients that linearly parametrize the model. From these, we retrieve a set of feasible link parameters (mass, position of center of mass, inertia) that is fundamental for more realistic dynamic simulations or when implementing in real time robot control laws using recursive NewtonEuler algorithms. The resulting problem is solved by means of an optimization method that incorporates constraints on the physical consistency of the dynamic parameters, including the triangle inequality of the link inertia tensors as well as other user-defined, possibly nonlinear constraints. The approach is developed for the increasingly popular Panda robot by Franka Emika, identifying for the first time its dynamic coefficients, an accurate joint friction model, and a set of feasible dynamic parameters. Validation of the identified dynamic model and of the retrieved feasible parameters is presented for the inverse dynamics problem using, respectively, a Lagrangian approach and Newton-Euler computations

Realeasy: Real-Time capable Simulation to Reality Domain Adaptation

We address the problem of insufficient quality of robot simulators to produce precise sensor readings for joint positions, velocities and torques. Realistic simulations of sensor readings are particularly important for real time robot control laws and for data intensive Reinforcement Learning of robot movements in simulation. We systematically construct two architectures based on Long Short-Term Memory to model the difference between simulated and real sensor readings for online and offline application. Our solution is easy to integrate into existing Robot Operating System frameworks and its formulation is neither robot nor task specific. The collected data set, the plug-and-play Realeasy model for the Panda robot and a reproducible real-time docker setup are shared alongside the code. We demonstrate robust behavior and transferability of the learned model between individual Franka Emika Panda robots. Our experiments show a reduction in torque mean squared error of at least one order of magnitude

Online velocity constraint adaptation for safe and efficient human-robot workspace sharing

Despite the many advances in collaborative robotics, collaborative robot control laws remain similar to the ones used in more standard industrial robots, significantly reducing the capabilities of the robot when in proximity to a human. Improving the efficiency of collaborative robots requires revising the control approaches and modulating online and in real-time the low-level control of the robot to strictly ensure the safety of the human while guaranteeing efficient task realization. In this work, an openly simple and fast optimization based joint velocity controller is proposed which modulates the joint velocity constraints based on the robot's braking capabilities and the separation distance. The proposed controller is validated on the 7 degrees-of-freedom Franka Emika Panda collaborative robot

Online velocity constraint adaptation for safe and efficient human-robot workspace sharing

International audienceDespite the many advances in collaborative robotics, collaborative robot control laws remain similar tothe ones used in more standard industrial robots, significantly reducing the capabilities of the robot when in proximity toa human. Improving the efficiency of collaborative robots requires revising the control approaches and modulating onlineand in real-time the low-level control of the robot to strictly ensure the safety of the human while guaranteeing efficienttask realization. In this work, an openly simple and fast optimization based joint velocity controller is proposed whichmodulates the joint velocity constraints based on the robot’s braking capabilities and the separation distance. The proposedcontroller is validated on the 7 degrees-of-freedom Franka Emika Panda collaborative robot

Enhancing fluency and productivity in human-robot collaboration through online scaling of dynamic safety zones

Industrial collaborative robotics is promising for manufacturing activities where the presence of a robot alongside a human operator can improve operator’s working conditions, flexibility, and productivity. A collaborative robotic application has to guarantee not only safety of the human operator, but also fluency in the collaboration, as well as performance in terms of productivity and task time. In this paper, we present an approach to enhance fluency and productivity in human-robot collaboration through online scaling of dynamic safety zones. A supervisory controller runs online safety checks between bounding volumes enclosing robot and human to identify possible collision dangers. To optimize the sizes of safety zones enclosing the manipulator, the method minimizes the time of potential stop trajectories considering the robot dynamics and its torque constraints, and leverages the directed speed of the robot parts with respect to the human. Simulations and experimental tests on a seven-degree-of-freedom robotic arm verify the effectiveness of the proposed approach, and collaborative fluency metrics show the benefits of the method with respect to existing approaches

Intent Classification during Human-Robot Contact

Robots are used in many areas of industry and automation. Currently, human safety is ensured through physical separation and safeguards. However, there is increasing interest in allowing robots and humans to work in close proximity or on collaborative tasks. In these cases, there is a need for the robot itself to recognize if a collision has occurred and respond in a way which prevents further damage or harm. At the same time, there is a need for robots to respond appropriately to intentional contact during interactive and collaborative tasks. This thesis proposes a classification-based approach for differentiating between several intentional contact types, accidental contact, and no-contact situations. A dataset is de- veloped using the Franka Emika Panda robot arm. Several machine learning algorithms, including Support Vector Machines, Convolutional Neural Networks, and Long Short-Term Memory Networks, are applied and used to perform classification on this dataset. First, Support Vector Machines were used to perform feature identification. Compar- isons were made between classification on raw sensor data compared to data calculated from a robot dynamic model, as well as between linear and nonlinear features. The results show that very few features can be used to achieve the best results, and accuracy is highest when combining raw data from sensors with model-based data. Accuracies of up to 87% were achieved. Methods of performing classification on the basis of each individual joint, compared to the whole arm, are tested, and shown not to provide additional benefits. Second, Convolutional Neural Networks and Long Short-Term Memory Networks were evaluated for the classification task. A simulated dataset was generated and augmented with noise for training the classifiers. Experiments show that additional simulated and augmented data can improve accuracy in some cases, as well as lower the amount of real- world data required to train the networks. Accuracies up to 93% and 84% we achieved by the CNN and LSTM networks, respectively. The CNN achieved an accuracy of 87% using all real data, and up to 93% using only 50% of the real data with simulated data added to the training set, as well as with augmented data. The LSTM achieved an accuracy of 75% using all real data, and nearly 80% accuracy using 75% of real data with augmented simulation data