| 1. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
-
Enhancing digital human motion planning of assembly tasks through dynamics and optimal control
- 2016
-
Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 44, s. 20-25
-
Konferensbidrag (refereegranskat)abstract
- Better operator ergonomics in assembly plants reduce work related injuries, improve quality, productivity and reduce cost. In this paper we investigate the importance of modeling dynamics when planning for manual assembly operations. We propose modeling the dynamical human motion planning problem using the Discrete Mechanics and Optimal Control (DMOC) method, which makes it possible to optimize with respect to very general objectives. First, two industrial cases are simulated using a quasi-static inverse kinematics solver, demonstrating problems where this approach is sufficient. Then, the DMOC-method is used to solve for optimal trajectories of a lifting operation with dynamics. The resulting trajectories are compared to a steady state solution along the same path, indicating the importance of using dynamics.
|
|
| 2. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
-
Exploiting sparsity in the discrete mechanics and optimal control method with application to human motion planning
- 2015
-
Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. - 9781467381833 ; , s. 769-774
-
Konferensbidrag (refereegranskat)abstract
- The discrete equations of motion derived using a variational principle are particularly attractive to be used in numerical optimal control methods. This is mainly because: i) they exhibit excellent energy behavior, ii) they extend gracefully to systems with holonomic constraints and iii) they admit compact representation of the discrete state space. In this paper we propose the use of sparse finite differencing techniques for the Discrete Mechanics and Optimal Control method. In particular we show how to efficiently construct estimates of the Jacobian and Hessian matrices when the dynamics of the optimal control problem is discretized using a variational integrator. To demonstrate the effectiveness of this scheme we solve a human motion planning problem of an industrial assembly task, modeled as a multibody system consisting of more than one hundred degrees of freedom.
|
|
| 3. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
-
Inverse Dynamics for Discrete Geometric Mechanics of Multibody Systems with Application to Direct Optimal Control
- 2018
-
Ingår i: Journal of Computational and Nonlinear Dynamics. - : ASME International. - 1555-1423 .- 1555-1415. ; 13:10
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present efficient algorithms for computation of the residual of the constrained discrete Euler-Lagrange (DEL) equations of motion for tree structured, rigid multibody systems. In particular, we present new recursive formulas for computing partial derivatives of the kinetic energy. This enables us to solve the inverse dynamics problem of the discrete system with linear computational complexity. The resulting algorithms are easy to implement and can naturally be applied to a very broad class of multibody systems by imposing constraints on the coordinates by means of Lagrange multipliers. A comparison is made with an existing software package, which shows a drastic improvement in computational efficiency. Our interest in inverse dynamics is primarily to apply direct transcription optimal control methods to multibody systems. As an example application, we present a digital human motion planning problem, which we solve using the proposed method. Furthermore, we present detailed descriptions of several common joints, in particular singularity-free models of the spherical joint and the rigid body joint, using the Lie groups of unit quaternions and unit dual quaternions, respectively.
|
|
| 4. |
- Cronrath, Constantin Christian Justin, 1990, et al.
(författare)
-
Energy reduction in paint shops through energy-sensitive on-off control
- 2016
-
Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. - 9781509024094 ; , s. 1282-1288
-
Konferensbidrag (refereegranskat)abstract
- Energy efficiency is the key for a sustainable manufacturing. However, energy efficiency measures often struggle with barriers, which inhibit their implementation. Environmental discrete event simulation is an approach increasingly discussed in research to overcome such barriers. Paint shops, which are responsible for 50-70% of an assembly plant's energy utilization in vehicular manufacturing, are seldom considered in this research, though. Therefore, the specific requirements on an energy consumption model for painting systems were investigated and implemented in simulation software. In addition, an energy-sensitive algorithm is proposed to reveal energy efficiency potentials based on an on-off control strategy. The result is a comprehensive simulation concept, that contributes to the removal of energy efficiency barriers by enabling a detailed evaluation of improvement measures and by indicating worthwhile saving potentials. A case study for a typical paint shop shows that the total energy saving potential is 7% in total, corresponding to more than 300 MWh of annual savings. © 2016 IEEE.
|
|
| 5. |
- Cronrath, Constantin, 1990, et al.
(författare)
-
Enhancing digital twins through reinforcement learning
- 2019
-
Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. ; 2019-August, s. 293-298
-
Konferensbidrag (refereegranskat)abstract
- Digital Twins are core enablers of smart and autonomous manufacturing systems. Although they strive to represent their physical counterpart as accurately as possible, slight model or data errors will remain. We present an algorithm to compensate for those residual errors through Reinforcement Learning (RL) and data fed back from the manufacturing system. When learning, the Digital Twin acts as teacher and safety policy to ensure minimal performance. We test the algorithm in a sheet metal assembly context, in which locators of the fixture are optimally adjusted for individual assemblies. Our results show a fast adaption and improved performance of the autonomous system.
|
|
| 6. |
- Gleeson, Daniel, 1988, et al.
(författare)
-
Implementation of a Rapidly Executing Robot Controller
- 2019
-
Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. ; 2019-August, s. 1341-1346
-
Konferensbidrag (refereegranskat)abstract
- This article describes the implementation of a high level and rapidly executing robot controller. It can be used to emulate the trajectory a robot will follow, given a set of robot motion commands. A geometric path parameterisation is used, which is tuned to match observed controller behaviour. It is also shown how this path is time stamped, while fulfilling velocity and acceleration constraints to produce a robot trajectory. The behaviour of the controller can emulate the behaviour of official controllers from robot vendors by parameter identification. The trajectory has been compared to an ABB 6640 robot, using an ABB virtual controller environment, and to sampled robot trajectory experiments of the KUICA robots KR 30-3 and IIWA. Good agreement with the geometric trajectories of the ABB robot and the IIWA robot has been achieved. For the KR 30-3 robot the proposed method does not fully capture the observed controller behaviour, but the resulting deviations are still within fractions of a degree for the test trajectories used.
|
|
| 7. |
- Gleeson, Daniel, 1988, et al.
(författare)
-
Optimizing robot trajectories for automatic robot code generation
- 2015
-
Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. - 9781467381833 ; , s. 495-500
-
Konferensbidrag (refereegranskat)abstract
- In manufacturing industry, the automation of robot trajectory planning and robot code generation lowers the development and assessment times of new products and models, increasing the flexibility of a robotic production line. This is of increasing importance in a number of industries where new products and new models are constantly being developed. This paper presents a method that automatically generates robot code for collision free trajectories. Starting with a collision free piecewise linear joint space trajectory, a direct transcription optimal control method is used, iteratively, to improve the trajectory while maintaining a desired clearance. The final solution is a collision free robot trajectory defined by a set of parameters, e.g. joint space via points and TCP-zone radii, that can be used to automatically generate functional RAPID code for an industrial robot. The algorithm is designed to be easily extendable. For example, by changing the constraints on the trajectory or by including energy consumption as an objective. A successful test of the algorithm has been carried out on an industrial stud welding station using the ABB virtual controller, indicating a 10% improvement in motion time.
|
|
| 8. |
- Gleeson, Daniel, 1988, et al.
(författare)
-
Towards Energy Optimization using Trajectory Smoothing and Automatic Code Generation for Robotic Assembly
- 2016
-
Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 44, s. 341-346
-
Konferensbidrag (refereegranskat)abstract
- In automated industrial production, the efficiency of robotic motions directly affects both the final throughput and the energy consumption. By simulating and optimizing robot trajectories, cycle times and energy consumption can be lowered, or redundant robots can be detected. Here a polynomial basis function trajectory parametrization is presented, which enables direct export to executable robot code, and reduces the number of variables in the optimization problem. The algorithm finds time-optimal trajectories, while including collision avoidance and fulfilling joint, velocity and acceleration limitations. Applied torques are used as an approximation of the energy consumption to analyse the smooth trajectories, and successful tests show potential reductions of 10% for a standard industrial robot stud welding station.
|
|
| 9. |
- Glorieux, Emile, 1989-, et al.
(författare)
-
Constructive cooperative coevolution for large-scale global optimisation
- 2017
-
Ingår i: Journal of Heuristics. - : Springer Science and Business Media LLC. - 1381-1231 .- 1572-9397. ; 23:6, s. 449-469
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the Constructive Cooperative Coevolutionary ( C3C3 ) algorithm, applied to continuous large-scale global optimisation problems. The novelty of C3C3 is that it utilises a multi-start architecture and incorporates the Cooperative Coevolutionary algorithm. The considered optimisation problem is decomposed into subproblems. An embedded optimisation algorithm optimises the subproblems separately while exchanging information to co-adapt the solutions for the subproblems. Further, C3C3 includes a novel constructive heuristic that generates different feasible solutions for the entire problem and thereby expedites the search. In this work, two different versions of C3C3 are evaluated on high-dimensional benchmark problems, including the CEC'2013 test suite for large-scale global optimisation. C3C3 is compared with several state-of-the-art algorithms, which shows that C3C3 is among the most competitive algorithms. C3C3 outperforms the other algorithms for most partially separable functions and overlapping functions. This shows that C3C3 is an effective algorithm for large-scale global optimisation. This paper demonstrates the enhanced performance by using constructive heuristics for generating initial feasible solutions for Cooperative Coevolutionary algorithms in a multi-start framework.
|
|
| 10. |
- Glorieux, Emile, 1989-, et al.
(författare)
-
Constructive cooperative coevolutionary optimisation for interacting production stations
- 2015
-
Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 78:1-4, s. 673-688
-
Tidskriftsartikel (refereegranskat)abstract
- Optimisation of the control function for multiple automated interacting production stations is a complex problem, even for skilled and experienced operators or process planners. When using mathematical optimisation techniques, it often becomes necessary to use simulation models to represent the problem because of the high complexity (i.e. simulation-based optimisation). Standard optimisation techniques are likely to either exceed the practical time frame or under-perform compared to the manual tuning by the operators or process planners. This paper presents the Constructive cooperative coevolutionary (C3) algorithm, which objective is to enable effective simulation-based optimisation for the control of automated interacting production stations within a practical time frame. C3 is inspired by an existing cooperative coevolutionary algorithm. Thereby, it embeds an algorithm that optimises subproblems separately. C3 also incorporates a novel constructive heuristic to find good initial solutions and thereby expedite the optimisation. In this work, two industrial optimisation problems, involving interaction production stations, with different sizes are used to evaluate C3. The results illustrate that with C3, it is possible to optimise these problems within a practical time frame and obtain a better solution compared to manual tuning.
|
|
