| 1. |
- Hellström, Thomas, 1956-, et al.
(författare)
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A Java-based middleware for control and sensing in mobile robotics
- 2008
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Ingår i: International Conference on Intelligent Automation and Robotics 2008. - 9789889867102 ; , s. 649-654
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Konferensbidrag (refereegranskat)abstract
- Many of the existing mobile-robot software packages do not include handling of sensors and actuators in a sufficiently systematic and uniform way, as described later in this section. The software framework proposed in this paper, denoted NAV2000, addresses the specific need for interchangeability of components in robotics. At the lowest level, sensors, and sometimes also actuators, often have to be replaced by similar, yet not identical, components. At a higher level, the target vehicle often changes during the work process. The presented software provides a framework that supports these replacements and allows configurations of sensors, actuators, and target machines to be specified and manipulated in an efficient manner. The system can be distributed over a network of computers if some software modules require more computing power, i.e. more hardware can be added to the system without any software changes. To accomplish sufficient monitoring of the system's health, a dedicated system keeps track of all software modules. The system uses logfiles to enable convenient debugging and performance analysis of hardware and software modules. The software has been developed as part of, and is currently in use in, a R&D-project for an autonomous path-tracking forest machine.
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| 2. |
- Billing, Erik, 1981-, et al.
(författare)
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A formalism for learning from demonstration
- 2010
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Ingår i: Paladyn - Journal of Behavioral Robotics. - : De Gruyter Open. - 2080-9778 .- 2081-4836. ; 1:1, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes and formalizes the concepts and assumptions involved in Learning from Demonstration (LFD), a common learning technique used in robotics. LFD-related concepts like goal, generalization, and repetition are here defined, analyzed, and put into context. Robot behaviors are described in terms of trajectories through information spaces and learning is formulated as mappings between some of these spaces. Finally, behavior primitives are introduced as one example of good bias in learning, dividing the learning process into the three stages of behavior segmentation, behavior recognition, and behavior coordination. The formalism is exemplified through a sequence learning task where a robot equipped with a gripper arm is to move objects to specific areas. The introduced concepts are illustrated with special focus on how bias of various kinds can be used to enable learning from a single demonstration, and how ambiguities in demonstrations can be identified and handled.
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| 3. |
- Billing, Erik, 1981-, et al.
(författare)
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Behavior recognition for learning from demonstration
- 2010
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Ingår i: 2010 IEEE International Conference on Robotics and Automation. - : IEEE. - 9781424450404 - 9781424450381 ; , s. 866-872
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Konferensbidrag (refereegranskat)abstract
- Two methods for behavior recognition are presented and evaluated. Both methods are based on the dynamic temporal difference algorithm Predictive Sequence Learning (PSL) which has previously been proposed as a learning algorithm for robot control. One strength of the proposed recognition methods is that the model PSL builds to recognize behaviors is identical to that used for control, implying that the controller (inverse model) and the recognition algorithm (forward model) can be implemented as two aspects of the same model. The two proposed methods, PSLE-Comparison and PSLH-Comparison, are evaluated in a Learning from Demonstration setting, where each algorithm should recognize a known skill in a demonstration performed via teleoperation. PSLH-Comparison produced the smallest recognition error. The results indicate that PSLH-Comparison could be a suitable algorithm for integration in a hierarchical control system consistent with recent models of human perception and motor control.
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| 4. |
- Billing, Erik, 1981-, et al.
(författare)
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Behavior recognition for segmentation of demonstrated tasks
- 2008
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Ingår i: IEEE SMC International Conference on Distributed Human-Machine Systems (DHMS). - 9788001040270
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Konferensbidrag (refereegranskat)abstract
- One common approach to the robot learning technique Learning From Demonstration, is to use a set of pre-programmed skills as building blocks for more complex tasks. One important part of this approach is recognition of these skills in a demonstration comprising a stream of sensor and actuator data. In this paper, three novel techniques for behavior recognition are presented and compared. The first technique is function-oriented and compares actions for similar inputs. The second technique is based on auto-associative neural networks and compares reconstruction errors in sensory-motor space. The third technique is based on S-Learning and compares sequences of patterns in sensory-motor space. All three techniques compute an activity level which can be seen as an alternative to a pure classification approach. Performed tests show how the former approach allows a more informative interpretation of a demonstration, by not determining "correct" behaviors but rather a number of alternative interpretations.
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| 5. |
- Billing, Erik, 1981-, et al.
(författare)
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Formalising learning from demonstration
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The paper describes and formalizes the concepts and assumptions involved in Learning from Demonstration (LFD), a common learning technique used in robotics. Inspired by the work on planning and actuation by LaValle, common LFD-related concepts like goal, generalization, and repetition are here defined, analyzed, and put into context. Robot behaviors are described in terms of trajectories through information spaces and learning is formulated as the mappings between some of these spaces. Finally, behavior primitives are introduced as one example of useful bias in the learning process, dividing the learning process into the three stages of behavior segmentation, behavior recognition, and behavior coordination.
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| 6. |
- Billing, Erik, 1981-, et al.
(författare)
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Model-free learning from demonstration
- 2010
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Ingår i: ICAART 2010 - Proceedings of the international conference on agents and artificial intelligence. - Portugal : INSTICC. - 9789896740221 ; , s. 62-71
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Konferensbidrag (refereegranskat)abstract
- A novel robot learning algorithm called Predictive Sequence Learning (PSL) is presented and evaluated. PSL is a model-free prediction algorithm inspired by the dynamic temporal difference algorithm S-Learning. While S-Learning has previously been applied as a reinforcement learning algorithm for robots, PSL is here applied to a Learning from Demonstration problem. The proposed algorithm is evaluated on four tasks using a Khepera II robot. PSL builds a model from demonstrated data which is used to repeat the demonstrated behavior. After training, PSL can control the robot by continually predicting the next action, based on the sequence of passed sensor and motor events. PSL was able to successfully learn and repeat the first three (elementary) tasks, but it was unable to successfully repeat the fourth (composed) behavior. The results indicate that PSL is suitable for learning problems up to a certain complexity, while higher level coordination is required for learning more complex behaviors.
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| 7. |
- Billing, Erik, 1981-, et al.
(författare)
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Predictive learning from demonstration
- 2011. - 1
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Ingår i: Agents and artificial Intelligence. - Berlin : Springer Verlag. - 9783642198892 - 9783642198908 ; , s. 186-200
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Bokkapitel (refereegranskat)abstract
- A model-free learning algorithm called Predictive Sequence Learning (PSL) is presented and evaluated in a robot Learning from Demonstration (LFD) setting. PSL is inspired by several functional models of the brain. It constructs sequences of predictable sensory-motor patterns, without relying on predefined higher-level concepts. The algorithm is demonstrated on a Khepera II robot in four different tasks. During training, PSL generates a hypothesis library from demonstrated data. The library is then used to control the robot by continually predicting the next action, based on the sequence of passed sensor and motor events. In this way, the robot reproduces the demonstrated behavior. PSL is able to successfully learn and repeat three elementary tasks, but is unable to repeat a fourth, composed behavior. The results indicate that PSL is suitable for learning problems up to a certain complexity, while higher level coordination is required for learning more complex behaviors.
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| 8. |
- Billing, Erik, 1981-, et al.
(författare)
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Predictive Learning in Context
- 2010
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Ingår i: Proceedings of the tenth international conference on epigenetic robotics. - Lund, Sweden : Lund University. - 9789197738095 ; , s. 157-158
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Konferensbidrag (refereegranskat)
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| 9. |
- Billing, Erik, 1981-, et al.
(författare)
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Robot learning from demonstration using predictive sequence learning
- 2012
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Ingår i: Robotic systems. - Kanpur, India : IN-TECH. - 9789533079417 ; , s. 235-250
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Bokkapitel (refereegranskat)abstract
- In this chapter, the prediction algorithm Predictive Sequence Learning (PSL) is presented and evaluated in a robot Learning from Demonstration (LFD) setting. PSL generates hypotheses from a sequence of sensory-motor events. Generated hypotheses can be used as a semi-reactive controller for robots. PSL has previously been used as a method for LFD, but suffered from combinatorial explosion when applied to data with many dimensions, such as high dimensional sensor and motor data. A new version of PSL, referred to as Fuzzy Predictive Sequence Learning (FPSL), is presented and evaluated in this chapter. FPSL is implemented as a Fuzzy Logic rule base and works on a continuous state space, in contrast to the discrete state space used in the original design of PSL. The evaluation of FPSL shows a significant performance improvement in comparison to the discrete version of the algorithm. Applied to an LFD task in a simulated apartment environment, the robot is able to learn to navigate to a specific location, starting from an unknown position in the apartment.
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| 10. |
- Billing, Erik, 1981-, et al.
(författare)
-
Robot learning from demonstration using predictive sequence learning
- 2011
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Ingår i: Robotic systems. - Kanpur, India : IN-TECH. - 9789533079417 ; , s. 235-250
-
Bokkapitel (refereegranskat)abstract
- In this chapter, the prediction algorithm Predictive Sequence Learning (PSL) is presented and evaluated in a robot Learning from Demonstration (LFD) setting. PSL generates hypotheses from a sequence of sensory-motor events. Generated hypotheses can be used as a semi-reactive controller for robots. PSL has previously been used as a method for LFD, but suffered from combinatorial explosion when applied to data with many dimensions, such as high dimensional sensor and motor data. A new version of PSL, referred to as Fuzzy Predictive Sequence Learning (FPSL), is presented and evaluated in this chapter. FPSL is implemented as a Fuzzy Logic rule base and works on a continuous state space, in contrast to the discrete state space used in the original design of PSL. The evaluation of FPSL shows a significant performance improvement in comparison to the discrete version of the algorithm. Applied to an LFD task in a simulated apartment environment, the robot is able to learn to navigate to a specific location, starting from an unknown position in the apartment.
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| 11. |
- Billing, Erik, 1981-, et al.
(författare)
-
Simultaneous control and recognition of demonstrated behavior
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A method for Learning from Demonstration (LFD) is presented and evaluated on a simulated Robosoft Kompai robot. The presented algorithm, called Predictive Sequence Learning (PSL), builds fuzzy rules describing temporal relations between sensory-motor events recorded while a human operator is tele-operating the robot. The generated rule base can be used to control the robot and to predict expected sensor events in response to executed actions. The rule base can be trained under different contexts, represented as fuzzy sets. In the present work, contexts are used to represent different behaviors. Several behaviors can in this way be stored in the same rule base and partly share information. The context that best matches present circumstances can be identified using the predictive model and the robot can in this way automatically identify the most suitable behavior for precent circumstances. The performance of PSL as a method for LFD is evaluated with, and without, contextual information. The results indicate that PSL without contexts can learn and reproduce simple behaviors. The system also successfully identifies the most suitable context in almost all test cases. The robot's ability to reproduce more complex behaviors, with partly overlapping and conflicting information, significantly increases with the use of contexts. The results support a further development of PSL as a component of a dynamic hierarchical system performing control and predictions on several levels of abstraction.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Hellström, Thomas, 1956-, et al.
(författare)
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Autonomous forest vehicles : historic, envisioned, and state-of-the-art
- 2009
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Ingår i: International Journal of Forest Engineering. - 1494-2119 .- 1913-2220. ; 20:1, s. 33-38
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Tidskriftsartikel (refereegranskat)abstract
- The feasibility of using autonomous forest vehicles (which can be regarded as logical developments in the ongoing automation of forest machines), the systems that could be applied in them, their potential advantages and their limitations (in the foreseeable future) are considered here. The aims were to analyse: (1) the factors influencing the degree of automation in logging; (2) the technical principles that can be applied to autonomous forest machines, and (3) the feasibility of developing an autonomous path-tracking forest vehicle. A type of vehicle that is believed to have considerable commercial potential is an autonomous forwarder. The degree of automation is influenced by increased productivity, the machine operator as a bottle-neck, cost reduction, and environmental aspects. Technical principles that can be applied to autonomous forest vehicles are satellite navigation, wheel odometry, laser scanner and radar. A new path-tracking algorithm has been developed to reduce deviations from the desired path by utilizing the driver’s steering commands. The presented system has demonstrated both possibilities and difficulties associated with autonomous forest machines. It is in a field study shown that it is quite possible for them to learn and track a path previously demonstrated by an operator with an accuracy of 0.1m on flat ground and also to detect and avoid unexpected obstacles. Although the forest machine safely avoids obstacles, the study shows that further research in the field of obstacle avoidance is needed to optimize performance and ensure safe operation in a real forest environment.
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| 17. |
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| 18. |
- Hellström, Thomas, 1956-
(författare)
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Licens att döda
- 2012
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Ingår i: Forskning och framsteg. - 0015-7937. ; :5/6, s. 26-29
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 19. |
- Hellström, Thomas, 1956-
(författare)
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On the moral responsibility of military robots
- 2013
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Ingår i: Ethics and Information Technology. - Dordrecht : Springer. - 1388-1957 .- 1572-8439. ; 15:2, s. 99-107
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Tidskriftsartikel (refereegranskat)abstract
- This article discusses mechanisms and principles for assignment of moral responsibility to intelligent robots, with special focus on military robots. We introduce the concept autonomous power as a new concept, and use it to identify the type of robots that call for moral considerations. It is furthermore argued that autonomous power, and in particular the ability to learn, is decisive for assignment of moral responsibility to robots. As technological development will lead to robots with increasing autonomous power, we should be prepared for a future when people blame robots for their actions. It is important to, already today, investigate the mechanisms that control human behavior in this respect. The results may be used when designing future military robots, to control unwanted tendencies to assign responsibility to the robots. Independent of the responsibility issue, the moral quality of robots’ behavior should be seen as one of many performance measures by which we evaluate robots. How to design ethics based control systems should be carefully investigated already now. From a consequentialist view, it would indeed be highly immoral to develop robots capable of performing acts involving life and death, without including some kind of moral framework.
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| 20. |
- Hellström, Thomas, 1956-, et al.
(författare)
-
Real-time path planning using a simulator-in-the-loop
- 2009
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Ingår i: International Journal Vehicle Autonomous Systems. - : Inderscience. - 1471-0226. ; 7:1/2, s. 56-72
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the development of a real-time path planner for off-road vehicles using a simulator. The general idea with the presented system is to extend a standard path-tracking algorithm with a simulator that, in real-time, tries to predict collisions in a window forward in time. If a collision is predicted, the vehicle is stopped and a path-search phase is initiated. Variants of the original path are generated and simulated until a feasible path is found. The real vehicle then continues, now tracking the replanned path.
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| 21. |
- Irenaeus, Sandra, et al.
(författare)
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Intratumoral immunostimulatory AdCD40L gene therapy in patients with advanced solid tumors.
- 2021
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Ingår i: Cancer Gene Therapy. - : Springer Science and Business Media LLC. - 0929-1903 .- 1476-5500. ; 28:10-11, s. 1188-1197
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Tidskriftsartikel (refereegranskat)abstract
- AdCD40L is a replication-deficient virus carrying the gene for CD40 ligand which has previously been evaluated in patients with urothelial cancer and malignant melanoma. Herein, we present the results of repeated intratumoral injections of AdCD40L in seven patients with metastatic solid cancer. One patient who developed urothelial cancer derived from a renal transplant was treated with repeated injections of AdCD40L alone. The remaining patients suffered from cholangiocarcinoma, kidney, breast, rectal, or ovarian cancer and received AdCD40L repeatedly (4x) in combination with cyclophosphamide. The treatment was safe and generally well-tolerated. Two patients had clinical benefit of the treatment and one of them was accepted for re-treatment. Circulating proinflammatory cytokines were commonly increased after treatment, but save for TNFα, significances were not reached which could be due to the low number of patients. Similar to earlier findings in AdCD40L-treated melanoma patients, IL8 plasma levels were high in the present study. In conclusion, gene therapy by repeated intratumoral AdCD40L injections alone, or in combination with cyclophosphamide, is feasible and safe in patients with solid cancers. The potential of intratumoral CD40L gene transfer as treatment of cancer was illustrated by the clinical improvement in two out of seven patients.
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| 22. |
- Lindroos, Ola, et al.
(författare)
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Estimating the position of the harvester head : a key step towards the precision forestry of the future?
- 2015
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Ingår i: Croatian Journal of Forest Engineering. - Zagreb : University of Zagreb. - 1845-5719 .- 1848-9672. ; 36:2, s. 147-164
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Tidskriftsartikel (refereegranskat)abstract
- Modern harvesters are technologically sophisticated, with many useful features such as the ability to automatically measure stem diameters and lengths. This information is processed in real time to support value optimization when cutting stems into logs. It can also be transferred from the harvesters to centralized systems and used for wood supply management. Such information management systems have been available since the 1990s in Sweden and Finland, and are constantly being upgraded. However, data on the position of the harvester head relative to the machine are generally not recorded during harvesting. The routine acquisition and analysis of such data could offer several opportunities to improve forestry operations and related processes in the future. Here, we analyze the possible benefits of having this information, as well as the steps required to collect and process it. The benefits and drawbacks of different sensing technologies are discussed in terms of potential applications, accuracy and cost. We also present the results of preliminary testing using two of the proposed methods. Our analysis indicates that an improved scope for mapping and controlling machine movement is the main benefit that is directly related to the conduct of forestry operations. In addition, there are important indirect benefits relating to ecological mapping. Our analysis suggests that both of these benefits can be realized by measuring the angles of crane joints or the locations of crane segments and using the resulting information to compute the head's position. In keeping with our findings, two companies have recently introduced sensor equipped crane solutions.
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| 23. |
- Ringdahl, Ola, 1971-, et al.
(författare)
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Estimating wheel slip for a forest machine using RTK-DGPS
- 2012
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Ingår i: Journal of terramechanics. - : Elsevier BV. - 0022-4898 .- 1879-1204. ; 49:5, s. 271-279
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Tidskriftsartikel (refereegranskat)abstract
- Wheel slip may increase the risk for wheel rutting and tear up ground vegetation and superficial roots and thereby decreasing the bearing capacity of the ground, but also reducing the growth of nearby standing forest trees. With increased slip, more energy is consumed for making wheel ruts in the ground, with increased fuel consumption as a result. This paper proposes a novel method for measuring slip in an uneven forest terrain with an 8WD forestry machine. This is done by comparing the wheel velocity reported by the machine and velocity measured with an accurate DGPS system. Field tests with a forestry machine showed that slip could be calculated accurately with the suggested method. The tests showed that there was almost no slip on asphalt or gravel surfaces. In a forest environment, 10–15% slip was common. A future extension of the method enabling estimation of the slip of each wheel pair in the bogies is also suggested.
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| 24. |
- Ringdahl, Ola, 1971-, et al.
(författare)
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Path tracking in forest terrain by an autonomous forwarder
- 2011
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Ingår i: Scandinavian Journal of Forest Research. - : Taylor & Francis. - 0282-7581 .- 1651-1891. ; 26:4, s. 350-359
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Tidskriftsartikel (refereegranskat)abstract
- Autonomous navigation in forest terrain, where operation paths are rarely straight or flat and obstacles are common, is challenging. This paper evaluates a system designed to autonomously follow previously demonstrated paths in a forest environment without loading/unloading timber, a pre-step in the development of fully autonomous forwarders. The system consisted of a forwarder equipped with a high-precision global positioning system to measure the vehicle’s heading and position. A gyro was used to compensate for the influence of the vehicle’s roll and pitch. On an ordinary clear-cut forest area with numerous stumps, the vehicle was able to follow two different tracks, three times each at a speed of 1 m s-1, with a mean path tracking error of 6 and 7 cm, respectively. The error never exceeded 35 cm, and in 90% of the observations it was less than 14 and 15 cm, respectively. This accuracy is well within the necessary tolerance for forestry operations. In fact, a human operator would probably have a hard time following the track more accurately. Hence, the developed systems function satisfactorily when using previously demonstrated paths. However, further research on planning new paths in unknown unstructured terrain and on loading/unloading is required before timber transports can be fully automated.
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