Practical Implementation of a Dead Zone Inverse on a Hydraulic Wrist

2002 ◽  
Author(s):  
Joel D. Fortgang ◽  
Lynnane E. George ◽  
Wayne J. Book
Keyword(s):  
System Performance ◽  
Dead Zone ◽  
Open Loop ◽  
Practical Implementation ◽  
Successful Implementation ◽  
Control Loop ◽  
Ideal System ◽  
Order Of Magnitude ◽  
Break Points ◽  
The Dead

This paper presents practical aspects of implementing a dead zone inverse on a hydraulic wrist. A dead zone occurs over a range of small input values for which a system does not respond. It was desirable to use the most straightforward method available to achieve improved system performance while requiring the least amount of modification to the controller. Thus a fixed parameter dead zone inverse (DZI) was added to an existing proportional-integral (PI) controller. First, the parameters of the dead zone were characterized from open loop testing. These parameters are the break points, or input values between which the system does not respond at all, and the slope of the system’s response just outside the break points. The DZI augments the PI signal input to the plant, effectively adding or subtracting a constant equal to the size of the dead zone break points and scaling the input by its slope. Simulations predicted perfect system tracking, but implementation on the hardware revealed several practical issues. First, the dead zone slope parameters vary throughout the robot’s workspace. Overestimation can lead to non-ideal system performance, but the more extreme problem is underestimation, which effectively increases control loop gain and can lead to system instability. However, performance is not affected significantly unless these parameters are off by an order of magnitude. Overall the system performance is relatively robust to modeling errors in the slope parameters. The second issue is that noise can be magnified by the dead zone inverse and cause chattering. This problem was very noticeable in the wrist when the estimated dead zone break points were used in the DZI. This problem can be eliminated by reducing the dead zone break points or reintroducing a small artificial dead zone back into the control loop to envelope the expected noise level. The requirements for successful implementation of the DZI were found to be a basic characterization of the dead zone and an understanding of practical system issues that can be accentuated by its use. The effectiveness of the technique was tested through simulations and experiments on the wrist.

scholarly journals SHEAR-DRIVEN FLUSHING OF MICRO-TIDAL MARINAS

2012 ◽  
Vol 1 (33) ◽  
pp. 59 ◽  
Author(s):  
Enda Murphy ◽  
Mathieu Deiber ◽  
Sylvain Perrin
Keyword(s):  
Water Exchange ◽  
Dead Zone ◽  
Mixing Layer ◽  
Practical Implementation ◽  
Zone Model ◽  
Hydrodynamic Models ◽  
Water Renewal ◽  
Coastal Basins ◽  
The Dead ◽  
Peripheral Areas

Flushing or residence times are typically used as a first step in assessing water quality in marinas, harbours and coastal basins. Recent publications have offered guidance in relation to optimal marina basin and entrance geometries to help achieve rapid renewal. However, these guidelines have been developed for the particular case where water exchange is strongly tide-driven and are not widely applicable, particularly in micro-tidal regions. Where water renewal rates are dominated by shear-driven circulation and lateral transfer of momentum at the interface between the marina and the adjacent water body (i.e. a mixing layer), there is a strong analogy to groyne fields and other cases involving flows containing quasi-stagnant peripheral areas (dead zones). A series of numerical hydrodynamic models, developed in the TELEMAC system, were used to investigate the potential for the dead zone model of water exchange to provide a better means to guide optimization of basin and entrance geometry under such conditions. Real-world marina case studies were used to identify any constraints affecting the practical implementation of such an approach. The numerical model results demonstrate particular conditions under which the dead zone model of water exchange can be used effectively to optimize marina basin and entrance geometry.

High-Density Memristor-CMOS Ternary Logic Family

2020 ◽  
Author(s):  
Xiaoyuan Wang ◽  
Pengfei Zhou ◽  
Jason Eshraghian ◽  
Chih-Yang Lin ◽  
Herbert Ho-Ching Iu ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Practical Implementation ◽  
Switching Speed ◽  
High Data ◽  
Fast Switching ◽  
Data Density ◽  
Order Of Magnitude ◽  
High Transconductance ◽  
Logic Functions ◽  
Magnitude Improvement

<div>This paper presents the first experimental demonstration</div><div>of a ternary memristor-CMOS logic family. We systematically</div><div>design, simulate and experimentally verify the primitive</div><div>logic functions: the ternary AND, OR and NOT gates. These are then used to build combinational ternary NAND, NOR, XOR and XNOR gates, as well as data handling ternary MAX and MIN gates. Our simulations are performed using a 50-nm process which are verified with in-house fabricated indium-tin-oxide memristors, optimized for fast switching, high transconductance, and low current leakage. We obtain close to an order of magnitude improvement in data density over conventional CMOS logic, and a reduction of switching speed by a factor of 13 over prior state-of-the-art ternary memristor results. We anticipate extensions of this work can realize practical implementation where high data density is of critical importance.</div>

Improved Pole-placement Control with Feed-forward Dead Zone Compensation for Position Tracking of Electro-Pneumatic Actuator System Improved Pole-placement Control with Feed-forward Dead Zone Compensation for Position Tracking of Electro-Pneumatic Actuato

2021 ◽  
Vol 20 (2) ◽  
pp. 25-32
Author(s):  
Noorhazirah Sunar ◽  
Mohd Fua’ad Rahmat ◽  
Ahmad ‘Athif Mohd Fauzi ◽  
Zool Hilmi Ismail ◽  
Siti Marhanis Osman ◽  
...  
Keyword(s):  
Dead Zone ◽  
Pneumatic Actuator ◽  
Pole Placement ◽  
Position Tracking ◽  
Zone Model ◽  
Feed Forward ◽  
The Dead ◽  
Chattering Effect ◽  
Pole Placement Controller ◽  
Pole Placement Control

Dead-zone in the valve degraded the performances of the Electro-Pneumatic Actuator (EPA) system.  It makes the system difficult to control, become unstable and leads to chattering effect nearest desired position.  In order to cater this issue, the EPA system transfer function and the dead-zone model is identified by MATLAB SI toolbox and the Particle Swarm Optimization (PSO) algorithm respectively.  Then a parametric control is designed based on pole-placement approach and combine with feed-forward inverse dead-zone compensation.  To reduce chattering effect, a smooth parameter is added to the controller output.  The advantages of using these techniques are the chattering effect and the dead-zone of the EPA system is reduced.  Moreover, the feed-forward system improves the transient performance.  The results are compared with the pole-placement control (1) without compensator and (2) with conventional dead-zone compensator.  Based on the experimental results, the proposed controller reduced the chattering effect due to the controller output of conventional dead-zone compensation, 90% of the pole-placement controller steady-state error and 30% and 40% of the pole-placement controller with conventional dead-zone compensation settling time and rise time.

Piecewise Nonlinear Energy Sink

2015 ◽  
Author(s):  
Mohammad A. Al-Shudeifat
Keyword(s):  
Dead Zone ◽  
Linear Structure ◽  
Nonlinear Energy Sink ◽  
Viscous Damping ◽  
Nonlinear Stiffness ◽  
Flexible Design ◽  
Energy Inputs ◽  
Energy Sink ◽  
The Dead ◽  
Nonlinear Energy

Symmetric piecewise nonlinearities are employed here to design highly efficient nonlinear energy sink (NES). These symmetric piecewise nonlinearities are usually called in the literature as dead-zone nonlinearities. The proposed dead-zone NES includes symmetric clearance about its equilibrium position in which zero stiffness and linear viscous damping are incorporated. At the boundaries of the symmetric clearance, the NES is coupled to the linear structure by either linear or nonlinear stiffness components in addition to similar viscous damping to that in the clearance zone. By this flexible design of the dead-zone NES, we obtain a considerable enhancement in the NES efficiency at moderate and severe energy inputs. Moreover, the dead-zone NES is also found here through numerical simulations to be more robust for damping and stiffness variations than the linear absorber and some other types of NESs.

scholarly journals Experimental investigation on steady granular flows interacting with an obstacle down an inclined channel: study of the dead zone upstream from the obstacle. Application to interaction between dense snow avalanches and defence structures

2002 ◽  
Vol 2 (3/4) ◽  
pp. 187-191 ◽  
Author(s):  
T. Faug ◽  
P. Lachamp ◽  
M. Naaim
Keyword(s):  
Experimental Investigation ◽  
Dead Zone ◽  
Granular Flows ◽  
Friction Angle ◽  
Snow Avalanches ◽  
Zone Length ◽  
Inclined Channel ◽  
Zone Of Influence ◽  
The Dead ◽  
Obstacle Height

Abstract. An experimental investigation with dry granular flows passing over an obstacle down a rough inclined channel has been performed. The aim is to improve our understanding of the interaction between dense snow avalanches and defence structures. Specific attention was directed to the study of the zone of influence upstream from the obstacle, linked to the formation of a dead zone. The dead zone length L was systematically measured as a function of the obstacle height H and the channel inclination θ, for several discharges. In a whole range of channel inclinations, all the data are shown to collapse into a single curve when properly scaled. The scaling is based on the introduction of a theoretical deposit length (depending on H, θ and the internal friction angle of the material, φ) and a Froude number of the flow depending on the obstacle height.

Sign in / Sign up

Export Citation Format

Share Document