| 31. |
- Bengtsson, Kristofer, 1979, et al.
(författare)
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Towards Sequence Planning Based on Configurable Product and Manufacturing System Platforms
- 2010
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Ingår i: Proceedings of the 8th International Conference NordDesign 2010. - 9789163370649 ; Vol. 2, s. 467-476
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Konferensbidrag (refereegranskat)abstract
- Operation sequences are central in the interaction between product and manufacturing development. This is because the sequences create an understanding of how a product is manufactured. The high degree of complexity in managing and planning manufacturing operations during the development of a configurable product and manufacturing platform requires a new and more flexible sequence planning approach. By integrating configurable product and manufacturing system platform descriptions, product variance, manufacturing system flexibility, and product and manufacturing system complexity can all be efficiently adapted to each other by considering interrelated constraints. Such an integrated platform system also provides the information required to describe the operations needed to manufacture an instantiated product variant. This paper proposes an approach in which sequences are viewed based on the relations among self-contained operations, thus saving engineers from manually constructing sequences for each product variant. The sequences of operations related to, for example, the part flow for a specific platform configuration, robot operations or operator tasks can be automatically visualized through the use of different perspectives.
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| 32. |
- Bennulf, Mattias, 1992-, et al.
(författare)
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Goal-Oriented Process Plans in a Multiagent System for Plug & Produce
- 2021
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Ingår i: IEEE Transactions on Industrial Informatics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1941-0050 .- 1551-3203. ; 17:4, s. 2411-2421
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Tidskriftsartikel (refereegranskat)abstract
- This article presents a framework for Plug & Produce that makes it possible to use configurations rather than programming to adapt a manufacturing system for new resources and parts. This is solved by defining skills on resources, and goals for parts. To reach these goals, process plans are defined with a sequence of skills to be utilized without specifying specific resources. This makes it possible to separate the physical world from the process plans. When a process plan requires a skill, e.g., grip with a gripper resource, then that skill may require further skills, e.g., move with a robot resource. This creates a tree of connected resources that are not defined in the process plan. Physical and logical compatibility between resources in this tree is checked by comparing several parameters defined on the resources and the part. This article presents an algorithm together with a multiagent system framework that handles the search and matching required for selecting the correct resources.
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| 33. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
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Energy Efficient and Collision Free Motion of Industrial Robots using Optimal Control
- 2013
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Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089.
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Konferensbidrag (refereegranskat)abstract
- In a production plant for complex assembled products there could be up to several hundred of robots used for handling and joining operations. Thus, improvement in robot motions can have a huge impact on equipment utilization and energy consumption. These are two of the most important aspects of sustainability in a production system. Therefore, this paper presents an algorithm for generating efficient and collision free motion of industrial robots using path planning and direct transcription methods for numerical optimal control. As a measure of efficiency for moving between configurations we use a combination of the energy norm of the applied actuator torques and the cycle time. Velocity and torque limits are handled and modeled as hard constraints. However, more general problems can be solved by the same approach. Our novel algorithm solves the problem in three steps; (i) first a path planning algorithm calculates an initial collision free path, (ii) a convex optimal control problem is then formulated to follow this path, and finally (iii) a nonlinear optimal control problem is solved to iteratively improve the trajectory. The resulting trajectory is guaranteed to be collision free by restrictions in the configuration space based on a local sensitivity analysis. The algorithm has been successfully applied to several industrial cases demonstrating that the proposed method can be used effectively in practical applications.
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| 34. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
-
Enhancing digital human motion planning of assembly tasks through dynamics and optimal control
- 2016
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 44, s. 20-25
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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.
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| 35. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
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Exploiting sparsity in the discrete mechanics and optimal control method with application to human motion planning
- 2015
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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.
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| 36. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
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Inverse Dynamics for Discrete Geometric Mechanics of Multibody Systems with Application to Direct Optimal Control
- 2018
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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.
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| 37. |
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| 38. |
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