An Excavator Simulator for Determining the Principles of Operator Efficiency for Hydraulic Multi-DOF Systems

Presented at the 52nd National Conference on Fluid Power, Las Vegas, NV, USA, March 23-25, 2011.This paper discusses an excavator simulator constructed to evaluate the effects of human-machine interfaces (HMIs) on operator productivity. Simulation allows for standardization of the machine and environment and is less time consuming and cheaper than implementing the controller on the machine. The simulator discussed in this paper includes a realistic graphical display that exceeds the current academic simulators, audio, and a new soil model that accounts for all possible trajectories of the bucket through the soil. Two coordinated control schemes were implemented on the simulator and preliminary tests were performed to demonstrate that the simulator can be used to evaluate HMIs

Minimal-model for robust control design of large-scale hydraulic machines

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Suuri-inertiaisen puomin liikkeen hallinta

Tämä diplomityö tutkii suuri-inertiaisen puomin liikkeen hallintaa. Tutkittava kone on tela-alustainen kaatokasauskone, jonka kaatopää on massaltaan yli 3000 kilogrammaa. Tuo kaatopään suuri massa aiheuttaa merkittävää inertiaa ja haastetta puomin ohjaukseen. Työssä tutkittiin, kuinka saadaan parannettua sylinterin nopeuden ohjattavuutta ja hallintaa muuttuvissa tilanteissa verrattuna nykyiseen joystick-ohjattuun järjestelmään. Tutkimuksen pääasiallisena metodina käytetään simulointia. Aluksi Matlab ja Simulink ohjel-mistoilla luotiin systeemimalli. Tämä malli verifioitiin oikean koneen mittauksilla. Ohjausta varten kehitettiin kaksi uutta ohjausmallia ja niitä verrattiin nykyiseen toteutukseen. Nykyisessä toteutuksessa joystick-komento skaalataan suoraan virraksi. Ohjausvirtaan ei täten vaikuta vallitseva kuormasta aiheutuva paine. Laskuliikkeen ohjattavuus toimii silloin huonosti. Kehitetyistä ohjausmalleista myötäkytketty ohjaustapa huomioi paineen muutoksen kompensoinnin. Takaisinkytketty ohjaustapa säätää sylinterin nopeutta paineen muutoksen kompensoinnin rinnalla. Kehitettyjä ohjaustapoja testattiin kolmella erilaisella testitilanteella. Nosto- ja laskuliikkeen hitaalla rampituksella, muuttuvan nopeuden aiheuttavalla ohjauksella ja venttiiliyksikön offsetin muutoksen sisältävällä muuttuvan nopeuden aiheuttavalla ohjauksella. Testit tehtiin kahdella eri kuormituksella, joilla pyrittiin simuloimaan suurta inertiaa. Tulosten perusteella paineenmuutoksen kompensoinnin ja nopeussäädön sisältävä takaisinkytketty ohjaus on ylivoimaisesti paras ohjaustapa tutkituista tavoista. Tällä ohjaustavalla pystytään ottamaan huomioon venttiileiden karoissa esiintyviä toleranssi eroja, mutta päästiin myös lähemmäksi asetusarvoa muissakin testeissä

An Augmented Interaction Strategy For Designing Human-Machine Interfaces For Hydraulic Excavators

Lack of adequate information feedback and work visibility, and fatigue due to repetition have been identified as the major usability gaps in the human-machine interface (HMI) design of modern hydraulic excavators that subject operators to undue mental and physical workload, resulting in poor performance. To address these gaps, this work proposed an innovative interaction strategy, termed “augmented interaction”, for enhancing the usability of the hydraulic excavator. Augmented interaction involves the embodiment of heads-up display and coordinated control schemes into an efficient, effective and safe HMI. Augmented interaction was demonstrated using a framework consisting of three phases: Design, Implementation/Visualization, and Evaluation (D.IV.E). Guided by this framework, two alternative HMI design concepts (Design A: featuring heads-up display and coordinated control; and Design B: featuring heads-up display and joystick controls) in addition to the existing HMI design (Design C: featuring monitor display and joystick controls) were prototyped. A mixed reality seating buck simulator, named the Hydraulic Excavator Augmented Reality Simulator (H.E.A.R.S), was used to implement the designs and simulate a work environment along with a rock excavation task scenario. A usability evaluation was conducted with twenty participants to characterize the impact of the new HMI types using quantitative (task completion time, TCT; and operating error, OER) and qualitative (subjective workload and user preference) metrics. The results indicated that participants had a shorter TCT with Design A. For OER, there was a lower error probability due to collisions (PER1) with Design A, and lower error probability due to misses (PER2)with Design B. The subjective measures showed a lower overall workload and a high preference for Design B. It was concluded that augmented interaction provides a viable solution for enhancing the usability of the HMI of a hydraulic excavator

Haptic communication for remote mobile and manipulator robot operations in hazardous environments

Nuclear decommissioning involves the use of remotely deployed mobile vehicles and manipulators controlled via teleoperation systems. Manipulators are used for tooling and sorting tasks, and mobile vehicles are used to locate a manipulator near to the area that it is to be operated upon and also to carry a camera into a remote area for monitoring and assessment purposes. Teleoperations in hazardous environments are often hampered by a lack of visual information. Direct line of sight is often only available through small, thick windows, which often become discoloured and less transparent over time. Ideal camera locations are generally not possible, which can lead to areas of the cell not being visible, or at least difficult to see. Damage to the mobile, manipulator, tool or environment can be very expensive and dangerous. Despite the advances in the recent years of autonomous systems, the nuclear industry prefers generally to ensure that there is a human in the loop. This is due to the safety critical nature of the industry. Haptic interfaces provide a means of allowing an operator to control aspects of a task that would be difficult or impossible to control with impoverished visual feedback alone. Manipulator endeffector force control and mobile vehicle collision avoidance are examples of such tasks. Haptic communication has been integrated with both a Schilling Titan II manipulator teleoperation system and Cybermotion K2A mobile vehicle teleoperation system. The manipulator research was carried out using a real manipulator whereas the mobile research was carried out in simulation. Novel haptic communication generation algorithms have been developed. Experiments have been conducted using both the mobile and the manipulator to assess the performance gains offered by haptic communication. The results of the mobile vehicle experiments show that haptic feedback offered performance improvements in systems where the operator is solely responsible for control of the vehicle. However in systems where the operator is assisted by semi autonomous behaviour that can perform obstacle avoidance, the advantages of haptic feedback were more subtle. The results from the manipulator experiments served to support the results from the mobile vehicle experiments since they also show that haptic feedback does not always improve operator performance. Instead, performance gains rely heavily on the nature of the task, other system feedback channels and operator assistance features. The tasks performed with the manipulator were peg insertion, grinding and drilling.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Coordinated and Force-Feedback Control of Hydraulic Excavators

The human interface of a Caterpillar 325FB fellerbuncher was modi ed to allow the operator to use (i) a 5-DOF joystick, and (ii) a 6-DOF magneticallylevitated joystick with sti ness feedback. While the operator commanded the velocity of the endpoint, an onboard computer system managed total system power, solved the inverse kinematics, servoed the joint actuators, and controlled the magnetically-levitated joystick. It was found that there were signi cant bene ts to single joystick endpoint velocity control including smoothness of motion, less damage to product (trees), and ease of operation. Controlling joystick sti ness as a function of endpoint force, was found to be both a stable and e ective form of feedback for a system where joystick position maps to endpoint velocity. Two di erent hydraulic systems were implemented and evaluated. The rst used valve control, as in a standard excavator. The second used hydrostatic control, by variable displacement pumps, and was found to lead to lower power consumption and higher operating speeds. 1