| 1. |
- Riazi, Sarmad, 1986, et al.
(författare)
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Energy Optimization of Multi-robot Systems
- 2015
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Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. - 9781467381833 ; 2015-October, s. 1345-1350
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Konferensbidrag (refereegranskat)abstract
- This paper presents an optimization algorithm that has been able to save up to 45% of the energy consumption of an industrial multi-robot system. The tool Sequence Planner now includes these algorithms, focusing on minimizing energy consumption. The goal has been to reduce the energy consumption of individual robots and robots interacting in a work station, without changing the original paths or the total cycle time. The presented algorithms are based on an efficient and rapid nonlinear model for optimizing the sequences of operations and the motion trajectories. Smart simplification of the optimization problem together with innovative tools for logging data and executing the optimized trajectories on real robots has resulted in 18% to 45% saving of the energy consumption in the presented test scenarios.
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| 2. |
- Lennartson, Bengt, 1956, et al.
(författare)
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Modeling and Optimization of Hybrid Systems
- 2015
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 48:27, s. 351-357
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Konferensbidrag (refereegranskat)abstract
- In this paper a predicate transition model for discrete event systems is generalized to include continuous dynamics, and the result is a modular hybrid predicate transition model. Based on this model a hybrid Petri net, including explicit differential equations and shared variables, is also proposed. It is then shown how this hybrid Petri net model can be optimized based on a simple and robust nonlinear programming formulation. The procedure only assumes that desired sampled paths for a number of interacting moving devices are given, while originally equidistant time instances are adjusted to minimize a given criterion. This optimization of hybrid systems is also applied to a real robot station with interacting devices, which results in about 30\% reduction in energy consumption.
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| 3. |
- Lennartson, Bengt, 1956-, et al.
(författare)
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Modeling and Optimization of Hybrid Systems for the Tweeting Factory
- 2016
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Ingår i: IEEE Transactions on Automation Science and Engineering. - 1545-5955 .- 1558-3783. ; 13:1, s. 195-205
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a predicate transition model for discrete-event systems is generalized to include continuous dynamics, and the result is a modular hybrid predicate transition model. Based on this model, a hybrid Petri net including explicit differential equations and shared variables is also proposed. It is then shown how this hybrid Petri net model can be optimized based on a simple and robust nonlinear programming formulation. The procedure only assumes that desired sampled paths for a number of interacting moving devices are given, while originally equidistant time instances are adjusted to minimize a given criterion. This optimization of hybrid systems is also applied to a real robot station with interacting devices, which results in about 30% reduction in energy consumption. Moreover, a flexible online and event-based information architecture called the Tweeting Factory is proposed. Simple messages (tweets) from all kinds of equipment are combined into high-level knowledge, and it is demonstrated how this information architecture can be used to support optimization of robot stations.
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| 4. |
- Riazi, Sarmad, 1986, et al.
(författare)
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A Column Generation-Based Gossip Algorithm for Home Healthcare Routing and Scheduling Problems
- 2019
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Ingår i: IEEE Transactions on Automation Science and Engineering. - 1558-3783 .- 1545-5955. ; 16:1, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- Home healthcare (HHC) is a service that dispatches caregivers to people in need of healthcare who live in the home. The task assignment and route generation for caregivers can be formulated as an extension of the well-known vehicle routing problem with time windows (VRPTW). Currently, the most successful exact algorithms for VRPTW are based on a framework combining column generation (CG) and branching. Although such methods could be successful for HHC routing and scheduling problem (HHCRSP) as well, fast approximate algorithms are appealing, especially for large problems. In an early version of this paper, we employed a heuristic distributed gossip algorithm to solve HHCRSP. In this paper, we integrate the gossip algorithm with a local solver based on CG, which makes it an effective algorithm for larger problem instances. As it will be shown with extensive numerical experiments, for large problem instances, gossip-CG performs better than the pure CG. Note to Practitioners-The task of routing and scheduling caregivers for HHC providers can be formulated as a mathematical problem that is theoretically challenging to solve to optimality for large-scale problems involving many clients and caregivers. Although extensive research and tools for tackling this problem already exist, in practice, even in developed countries, it is still common to rely on schedules generated manually by staff. What we present in this paper is the summary of our theoretical work on tackling such problems. The benefit of the framework that we propose, the CG-based gossip method, is that it can be preempted at any time if the staff requires to obtain a good schedule as soon as possible. If ample time is available, one can let our algorithm to run for a longer period of time to generate even shorter routes.
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| 5. |
- Riazi, Sarmad, 1986, et al.
(författare)
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A Gossip Algorithm for Home Healthcare Scheduling and Routing Problems
- 2014
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 1474-6670. - 9783902823625 ; 19, s. 10754-10759
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Konferensbidrag (refereegranskat)abstract
- Many people in need of care still live in their homes, requiring the caretakers to travel to them. Assigning tasks to nurses (or caretakers) and scheduling their work plans is an NP-hard problem, which can be expressed as a vehicle routing problem with time windows (VRPTW) that includes additional problem-specific constraints. In this paper, we propose to solve the Home Healthcare Scheduling and Routing Problem (HHCRSP) by a distributed Gossip algorithm. We also apply an extended version called n-Gossip, which provides the required flexibility to balance optimality versus computational speed. We also introduce a relaxation on the optimality of the underlying solver in the Gossip, which speeds up the iterations of the Gossip algorithm, and helps to quickly obtain solutions with good quality.
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| 6. |
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| 7. |
- Riazi, Sarmad, 1986, et al.
(författare)
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Decomposition and distributed algorithms for home healthcare routing and scheduling problem
- 2017
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Ingår i: IEEE International Conference on Emerging Technologies and Factory Automation, ETFA. - 1946-0759 .- 1946-0740. ; , s. 1-7
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Konferensbidrag (refereegranskat)abstract
- Many people in need of care still live in their homes, requiring the caretakers to travel to them. Assigning the people to caretakers and generating their schedules can be formulated as a mixed integer linear programming problem (MILP) that inherits many features of the well-known vehicle routing problem with time windows (VRPTW). Currently, the most successful exact algorithms for VRPTW are based on branch and price framework, which combine column generation (CG) and branching. While these methods could be successful for Home Healthcare Routing and Scheduling Problem (HHCRSP) as well, fast approximate algorithms are appealing, especially for large problems. We recently employed a heuristic distributed gossip algorithm to solve HHCRSP. The method had the potential to provide approximate solutions for relatively large problem instances, but its effectiveness was limited to the performance of its local MILP solver. In this paper, we integrate the gossip algorithm with a local solver based on CG, which makes it an effective algorithm for larger problem instances. We also provide numerical experiments and complexity evaluations of the improved gossip algorithm (gossip-CG) with the standard gossip (gossip-MILP) and CG, and show that gossip-CG outperforms the pure CG in case of large problems.
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| 8. |
- Riazi, Sarmad, 1986, et al.
(författare)
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Energy and peak-power optimization of existing time-optimal robot trajectories
- 2016
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Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. - 9781509024094 ; 2016-November, s. 321-327
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Konferensbidrag (refereegranskat)abstract
- This paper, as an outcome of the EU project AREUS, heralds an optimization procedure that reduces up to 30% of energy consumption and up to 60% of peak-power for the trajectories that were tested on a real industrial robot. We have evaluated a number of cost functions and examined our algorithm for a variety of scenarios such as varying cycle times and single/two-robot cases. The significance of our work is not only in the impressive savings, simplicity of implementation and preserving path and cycle time, but also in the effort made to carry out the optimization and experiments in as realistic conditions as possible.
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| 9. |
- Riazi, Sarmad, 1986, et al.
(författare)
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Energy and Peak Power Optimization of Time-Bounded Robot Trajectories
- 2017
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Ingår i: IEEE Transactions on Automation Science and Engineering. - 1558-3783 .- 1545-5955. ; 14:2, s. 646-657
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Tidskriftsartikel (refereegranskat)abstract
- This paper, as an outcome of the EU project AREUS, heralds an optimization procedure that reduces up to 30% of energy consumption and up to 60% in peak power for the trajectories that have been tested on real industrial robots. We have evaluated a number of cost functions and tested our algorithm for a variety of scenarios such as varying cycle times, payloads, and single/multirobot cases in both ac- and dc-operated robot cells. The significance of our work is not only in the impressive savings, simplicity of implementation, and preserving path and cycle time, but also in the variety of test scenarios that include different kinds of KUKA robots. We have carried out the optimization and experiments in as realistic conditions as possible.
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| 10. |
- Riazi, Sarmad, 1986, et al.
(författare)
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Energy and Peak-power Optimization of Time-bounded Robot Trajectories
- 2017
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Ingår i: 2017 13TH IEEE CONFERENCE ON AUTOMATION SCIENCE AND ENGINEERING (CASE). - 2161-8070. - 9781509067817 ; , s. 1301-1301
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Konferensbidrag (refereegranskat)abstract
- This paper, as an outcome of the EU project AREUS, heralds an optimization procedure that reduces up to 30% of energy consumption and up to 60% in peak-power for the trajectories that were tested on a real industrial robot. We have evaluated a number of cost functions and tested our algorithm for a variety of scenarios such as varying cycle times, payloads, and single/two-robot cases. The significance of our work is not only in the impressive savings, simplicity of implementation and preserving path and cycle time, but also in the effort made to carry out the optimization and experiments in as realistic conditions as possible, and the guidelines we provide to achieve this.
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