This article proposes a specification-guided framework for control of nonlinear systems with linear temporal logic (LTL) specifications. In contrast with well-known abstraction-based methods, the proposed framework di...
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This article proposes a specification-guided framework for control of nonlinear systems with linear temporal logic (LTL) specifications. In contrast with well-known abstraction-based methods, the proposed framework directly characterizes the winning set, i.e., the set of initial conditions from which a given LTL formula can be realized, over the continuous state space of the system via a monotonic operator. Following this characterization, an algorithm is proposed to practically approximate the operator via an adaptive interval subdivision scheme, which yields a finite-memory control strategy. We show that the proposed algorithm is sound for full LTL specifications, and robustly complete for specifications recognizable by deterministic Buchi automaton (DBA), the latter in the sense that control strategies can be found whenever the given specification can be satisfied with additional bounded disturbances. Without having to compute and store the abstraction and the resulting product system with the DBA, the proposed method is more memory efficient, which is demonstrated by complexity analysis and performance tests. A preprocessing stage is also devised to reduce computational cost via a decomposition of the specification. We show that the proposed method can effectively solve real-world control problems, such as jet engine compressor control and motion planning for manipulators and mobile robots.
This paper proposes an online control framework for mobile robots to satisfy a complex mission given in the form of linear temporal logic (LTL) without colliding with moving obstacles in the environment. The proposed ...
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ISBN:
(纸本)9781665417143
This paper proposes an online control framework for mobile robots to satisfy a complex mission given in the form of linear temporal logic (LTL) without colliding with moving obstacles in the environment. The proposed framework consists of three modules named the static planner, the local collision avoidance, and the patcher. The static planner is synthesized by solving a parity game for a finite abstraction of the robot model based on a world map with static obstacles to fulfill the LTL task. The local collision avoidance module computes a set of safe controls that guarantees a safe distance between the moving objects. Both of the modules can be rigorously computed offline only once via formal methods. The patcher is activated whenever a moving obstacle is detected and modifies the static plan online for a short horizon by using only provably safe controls. The resulting modified strategy can guarantee collision-free motion without losing the ability to satisfy the LTL task. As opposed to using assume-guarantee type of LTL tasks, the proposed framework can handle the situations where obstacle movement is unpredictable.
Hybrid track/wheel-legged robots combine the advantages of wheel-based and leg-based locomotion, granting adaptability across varied terrains through efficient transitions between rolling and walking modes. However, a...
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Hybrid track/wheel-legged robots combine the advantages of wheel-based and leg-based locomotion, granting adaptability across varied terrains through efficient transitions between rolling and walking modes. However, automating these transitions remains a significant challenge. In this paper, we introduce a method designed for autonomous mode transition in a quadruped hybrid robot with a track/wheel-legged configuration, especially during step negotiation. Our approach hinges on a decision-making mechanism that evaluates the energy efficiency of both locomotion modes using a proposed energy-based criterion. To guarantee a smooth negotiation of steps, we incorporate two climbing gaits designated for the assessment of energy usage in walking locomotion. Simulation results validate the method's effectiveness, showing successful autonomous transitions across steps of diverse heights. Our suggested approach has universal applicability and can be modified to suit other hybrid robots of similar mechanical configuration, provided their locomotion energy performance is studied beforehand.
This paper describes the design, tuning, and extensive field testing of an admittance-based autonomous loading controller (ALC) for robotic excavation. Several iterations of the ALC were tuned and tested in fragmented...
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This paper describes the design, tuning, and extensive field testing of an admittance-based autonomous loading controller (ALC) for robotic excavation. Several iterations of the ALC were tuned and tested in fragmented rock pilessimilar to those found in operating minesby using both a robotic 1-tonne capacity Kubota R520S diesel-hydraulic surface loader and a 14-tonne capacity Atlas Copco ST14 underground load-haul-dump (LHD) machine. On the R520S loader, the ALC increased payload by 18% with greater consistency, although with more energy expended and longer dig times when compared with digging at maximum actuator velocity. On the ST14 LHD, the ALC took 61% less time to load 39% more payload when compared to a single manual operator. The manual operator made 28 dig attempts by using three different digging strategies, and had one failed dig. The tuned ALC made 26 dig attempts at 10and11MN target force levels. All 10 11MN digs succeeded while 6 of the 16 10MN digs failed. The results presented in this paper suggest that the admittance-based ALC is more productive and consistent than manual operators, but that care should be taken when detecting entry into the rock pile. (C) 2016 Wiley Periodicals, inc.
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