Modeling of controlled motion of semi-passively actuated SCARA-like robot

The controlled motion of a new structure of manipulator robot is under study. In comparison with the well-known SCARA robot the proposed robotic system has the following new features: in addition to powered drives it comprisesseveral unpowered (passive) spring-damper-like drives. An additional link has also been incorporated into the structure that gives the possibility to obtain a semipassively actuated closed-loop chain robot. Special emphasis is put on a study of the interaction between the controlling stimuli of the powered drives and the torquesexerted by the unpowered drives needed to provide the energy-optimal motion of the robot. Computer simulations have demonstrated the numerical efficiency of thedeveloped algorithms and have proved several advantages of the considered semipassively actuated closed-loop robot

Modeling of controlled motion of semi-passively actuated SCARA-like robot

The controlled motion of a new structure of manipulator robot is under study. In comparison with the well-known SCARA robot the proposed robotic system has the following new features: in addition to powered drives it comprisesseveral unpowered (passive) spring-damper-like drives. An additional link has also been incorporated into the structure that gives the possibility to obtain a semipassively actuated closed-loop chain robot. Special emphasis is put on a study of the interaction between the controlling stimuli of the powered drives and the torquesexerted by the unpowered drives needed to provide the energy-optimal motion of the robot. Computer simulations have demonstrated the numerical efficiency of thedeveloped algorithms and have proved several advantages of the considered semipassively actuated closed-loop robot

Optimisation of controlled motion of closed-loop chain manipulator robots with different degree and type of actuation

A number of energy-optimal control problems for a new structure of closed-loop manipulator robot are considered. We present methodology and algorithm that is suitable for solving optimization problems for manipulator robots with different degree and type of actuation. This methodology isbased on polynomial and Fourier series approximation of independently varying functions and conversion of the initial optimal control problem into the constrained parameter optimization problem. The methodology has been successfully used for optimization of under-, fully-, and overactuated robots having both external (powered) drives and internal (unpowered or passive) spring-damper-like drives. Comparison analysis of the simulation results of the obtained energy-optimal control processes fordifferent manipulator robots is presented

Regenerative braking for an electric vehicle with a high-speed drive at the front axle

The main contribution of this paper lies in the development of a novel front-to-rear axle brake force distribution strategy for the regenerative braking control of a vehicle with a high-speed electric drive unit at the front axle. The strategy adapts the brake proportioning to provide extended room for energy recuperation of the electric motor when the vehicle drivability and safety requirements permit. In detail, the strategy is adaptive to cornering intensity enabling the range to be further extended in real-world applications. The regenerative braking control features a brake blending control algorithm and a powertrain controller, which are decisive for enhancing the braking performance. Lastly, the regenerative braking control is implemented in the highfidelity simulation environment Simcenter Amesim, where system efficiency and regenerative brake performance are analysed. Results confirm that the designed regenerative braking greatly improves the effectiveness of energy recuperation for a front-wheel driven electric vehicle with a high-speed drive at the front axle. In conclusion, it is shown that it is feasible to use the high-speed drive with the proposed control design for regenerative braking

Experimental verification of understeer compensation by four wheel braking

This study is designed to validate a new approach to understeer mitigation chassis control, based on a particlemotion reference: parabolic path reference (PPR). Considering the scenario of excess entry speed into a curve,related to run-off-road crashes, the aim is that automatic braking minimizes lateral deviation from the target pathby using an optimal combination of deceleration, cornering forces and yaw moments. Previous simulationstudies showed that four-wheel braking can achieve this much better than a conventional form of yaw momentcontrol (DYC). The aim of this work is to verify this on a test track with an experimental vehicle, and to compareperformance with DYC and an uncontrolled vehicle. Experiments were performed with a front-wheel-drivepassenger vehicle equipped with an additional four identical brake callipers controlled via an electro-hydraulicbrake (EHB) system, enabling individual brake control. Minimizing the maximum deviation from the intendedcurve radius is the control objective. Feedback to the controller consists of the available steering wheel angle,wheel speeds, yaw rate and lateral acceleration sensors in the vehicle. Additional to these variables, also thevehicle position was logged using a GPS system. It was found that PPR is superior to DYC in reducing themaximum deviation from the intended path, confirming the trends previously found in simulations. Furthermore,the PPR concept is found to be inherently more stable than DYC since more brake force is applied to the outerwheels than the inner wheels throughout the manoeuvre. The experiments involve a first implementation of aPPR control which is not a fully closed-loop control intervention and tuned to a step steer (transition fromstraight to fixed-radius curve. This is the first study to explicitly and systematically evaluate this new approachto understeer mitigation. The approach is fundamentally different from common DYC and suggests the potentialfor a new generation of controllers based on trajectory control via chassis actuators

The FERRUM project: Transition probabilities for forbidden lines in [FeII] and experimental metastable lifetimes

Accurate transition probabilities for forbidden lines are important diagnostic parameters for low-density astrophysical plasmas. In this paper we present experimental atomic data for forbidden [FeII] transitions that are observed as strong features in astrophysical spectra. Aims: To measure lifetimes for the 3d^6(^3G)4s a ^4G_{11/2} and 3d^6(^3D)4s b ^4D_{1/2} metastable levels in FeII and experimental transition probabilities for the forbidden transitions 3d^7 a ^4F_{7/2,9/2}- 3d^6(^3G)4s a ^4G_{11/2}. Methods: The lifetimes were measured at the ion storage ring facility CRYRING using a laser probing technique. Astrophysical branching fractions were obtained from spectra of Eta Carinae, obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The lifetimes and branching fractions were combined to yield absolute transition probabilities. Results: The lifetimes of the a ^4G_{11/2} and the b ^4D_{1/2} levels have been measured and have the following values, 0.75(10) s and 0.54(3) s respectively. Furthermore, we have determined the transition probabilities for two forbidden transitions of a ^4F_{7/2,9/2}- a ^4G_{11/2} at 4243.97 and 4346.85 A. Both the lifetimes and the transition probabilities are compared to calculated values in the literature.Comment: 5 pages, accepted for publication in A&

Design and control of model based steering feel reference in an electric power assisted steering system

Electric Power Assisted Steering (EPAS) system is a current state of the art technology for providing the steering torque support. The interaction of the steering system with the driver is principally governed by the EPAS control method. This paper proposes a control concept for designing the steering feel with a model based approach. The reference steering feel is defined in virtual dynamics for tracking. The layout of the reference model and the control architecture is discussed at first and then the decoupling of EPAS motor dynamics using a feedback control is shown. An example of how a change in steering feel reference (as desired by the driver) creates a change in steering feedback is further exhibited. The ultimate goal is to provide the driver with a tunable steering feel. For this, the verification is performed in simulation environment

Direct yaw moment control for enhancing handling quality of lightweight electric vehicles with large load-to-curb weight ratio

In this paper a vehicle dynamics control system is designed to compensate the change in vehicle handling dynamics of lightweight vehicles due to variation in loading conditions and the effectiveness of the proposed design is verified by simulations and an experimental study using a fixed-base driving simulator. Considering the electrification of future mobility, the target vehicle of this research is a lightweight vehicle equipped with in-wheel motors that can generate an additional direct yaw moment by transverse distribution of traction forces to control vehicle yawing as well as side slip motions. Previously, the change in vehicle handling dynamics for various loading conditions have been analyzed by using a linear two-wheel vehicle model in planar motion and a control law of the DYC system based on feed-forward of front steering angular velocity and feedback of vehicle yaw rate. The feed-forward controller is derived based on the model following control with approximation of the vehicle dynamics to 1st-order transfer function. To make the determination of the yaw rate feedback gain model-based and adaptable to various vehicle velocity conditions, this paper selects a method where the yaw rate feedback gain in the DYC system is determined in a way that the steady-state yaw rate gain of the controlled loaded vehicle matches the gain of the unloaded vehicle. The DYC system is simulated in a single lane change maneuver to confirm the improved responsiveness of the vehicle while simulations of a double-lane change maneuver with a driver steering model confirms the effectiveness of the DYC system to support tracking control. Finally, the effectiveness of the proposed DYC system is also verified in an experimental study with ten human drivers using a fix-based driving simulator

A GPS velocity field for Fennoscandia and a consistent comparison to glacial isostatic adjustment models

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Temperature dependent c-axis hole mobilities in rubrene single crystals determined by time-of-flight

Hole mobilities (μ) in rubrene single crystals (space group Cmca) along the crystallographic c-axis have been investigated as a function of temperature and applied electric field by the time-of-fight method. Measurements demonstrate an inverse power law dependence on temperature, namely,μ=μ0T−n with n = 1.8, from room temperature down to 180 K. At 296 K, the average value of μ was found to be 0.29 cm2/Vs increasing to an average value of 0.70 cm2/Vs at 180 K. Below 180 K a decrease in mobility is observed with further cooling. Overall, these results confirm the anisotropic nature of transport in rubrene crystals as well as the generality of the inverse power law temperature dependence that is observed for field effect mobility measurements in the a-b crystal plane