scholarly journals Estimation and Closed-Loop Control of COG/ZMP in Biped Devices Blending CoP Measures and Kinematic Information

Robotics ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 89 ◽  
Author(s):  
Giuseppe Menga ◽  
Marco Ghirardi
Keyword(s):  
Closed Loop ◽  
Inverted Pendulum ◽  
Joint Angle ◽  
Center Of Pressure ◽  
Balance Control ◽  
External Disturbance ◽  
Practical Implementation ◽  
Complex Nature ◽  
Simple Relationship ◽  
Loop Control

The zero moment point ( Z M P ) and the linearized inverted pendulum model linking the Z M P to the center of gravity ( C O G ) have an important role in the control of the postural equilibrium (balance) of biped robots and lower-limb exoskeletons. A solution for balance real time control, closing the loop from the joint actual values of the C O G and Z M P , has been proposed by Choi. However, this approach cannot be practically implemented: While the Z M P actual value is available from the center of pressure ( C o P ) measured under the feet soles, the C O G is not measurable, but it can only be indirectly assessed from the joint-angle measures, the knowledge of the kinematics, and the usually poorly known weight distribution of the links of the chain. Finally, the possible presence of unknown external disturbance forces and the nonlinear, complex nature of the kinematics perturb the simple relationship between the Z M P and C O G in the linearized model. The aim of this paper is to offer, starting from Choi’s model, a practical implementation of closed-loop balance control fusing C o P and joint-angle measures, eliminating possible inconsistencies. In order to achieve this result, we introduce a model of the linearized inverted pendulum for an extended estimation, not only of C O G and Z M P , but also of external disturbances. This model is then used, instead of Choi’s equations, for estimation and balance control, using H ∞ theory. As the C O G information is recovered from the joint-angle measures, the identification of a statistically equivalent serial chain ( S E S C ) linking the C O G to the joint angles is also discussed.

A Novel Nonlinear and Adaptive Control of Grid Connected Inverters

2016 ◽  
Vol 25 (11) ◽  
pp. 1650132 ◽  
Author(s):  
Murat Karabacak
Keyword(s):  
Control System ◽  
High Performance ◽  
Closed Loop ◽  
External Disturbance ◽  
Lyapunov Stability Theory ◽  
Loop Control ◽  
Closed Loop Control System ◽  
Loop Control System ◽  
Dc Bus ◽  
Bus Voltage

In this study, a new nonlinear and adaptive state feedback controller is proposed for the control of grid connected inverters (GCIs). All the other parameters apart from direct current (DC) bus capacitor are considered uncertain in the design of proposed controller, without disadvantages of singularity and over-parametrization. Three-phase source currents, DC bus voltage and load current are supposed to be available for feedback in the closed loop control system. In this respect, the whole control loop, consisting of DC bus voltage and [Formula: see text]–[Formula: see text] axis current loops, is closed. It is important to highlight that closed loop DC voltage control cannot be achieved by most of nonlinear controllers proposed in literature. In the sense of Lyapunov stability theory, overall control system has the global asymptotic stability. Experimental results demonstrate that the proposed controller guarantees to asymptotically drive tracking errors to zero despite all parameter and external disturbance uncertainties. Results also verify that the proposed controller shows high performance and feasibility.

Self-feedback motion control for cable-driven parallel manipulators

2013 ◽  
Vol 228 (1) ◽  
pp. 77-89 ◽  
Author(s):  
Weihai Chen ◽  
Xiang Cui ◽  
Guilin Yang ◽  
Jingyuan Chen ◽  
Yan Jin
Keyword(s):  
Feedback Control ◽  
Motion Control ◽  
Control Algorithm ◽  
Closed Loop ◽  
Joint Angle ◽  
Time Derivative ◽  
Parallel Manipulators ◽  
The Self ◽  
Closed Loop Control ◽  
Loop Control

This article proposes a closed-loop control scheme based on joint-angle feedback for cable-driven parallel manipulators (CDPMs), which is able to overcome various difficulties resulting from the flexible nature of the driven cables to achieve higher control accuracy. By introducing a unique structure design that accommodates built-in encoders in passive joints, the seven degrees of freedom (7-DOF) CDPM can obtain joint angle values without external sensing devices, and it is used for feedback control together with a proper closed-loop control algorithm. The control algorithm has been derived from the time differential of the kinematic formulation, which relates the joint angular velocities to the time derivative of cable lengths. In addition, the Lyapunov stability theory and Monte Carlo method have been used to mathematically verify the self-feedback control law that has tolerance for parameter errors. With the aid of co-simulation technique, the self-feedback closed-loop control is applied on a 7-DOF CDPM and it shows higher motion accuracy than the one with an open-loop control. The trajectory tracking experiment on the motion control of the 7-DOF CDPM demonstrated a good performance of the self-feedback control method.

Research on Power Balance Control of Multi-Motor Driving Belt Conveyor System Based on Controlled Transmission Device

2015 ◽  
Vol 719-720 ◽  
pp. 400-404 ◽  
Author(s):  
Xin Huan Wang ◽  
Hong Wei Zhang ◽  
Zi Yi Fu
Keyword(s):  
Control System ◽  
Resource Sharing ◽  
Closed Loop ◽  
High Efficiency ◽  
Balance Control ◽  
Power Balance ◽  
Closed Loop Control ◽  
Belt Conveyor ◽  
Drive Power ◽  
Loop Control

According to the existing problems of driving equipment for belt conveyor, a novel design scheme of controlled transmission which uses hydraulic transmission system driving worm gear to control the output speed of planetary gear mechanism is proposed. The control strategy of multi-motor drive power balance which adopts master-slave structure is designed. The master driver adopts speed closed-loop control with current limiting and the slave drivers adopt power closed-loop control. The given power signal of slave pulley is decided by the master motor. The control system offers multiple communication interfaces which enable the belt conveyor to integrate in coal mine information platform and realize information resource sharing. The controlled transmission device and its power balance control system have characteristics of compact, reliable and high efficiency.

scholarly journals Distracting attention in phobic postural vertigo normalizes leg muscle activity and balance

Neurology ◽  
2016 ◽  
Vol 88 (3) ◽  
pp. 284-288 ◽  
Author(s):  
Max Wuehr ◽  
Thomas Brandt ◽  
Roman Schniepp
Keyword(s):  
Dual Task ◽  
Closed Loop ◽  
Center Of Pressure ◽  
Balance Control ◽  
Open Loop ◽  
Body Sway ◽  
Healthy Controls ◽  
Phobic Postural Vertigo ◽  
Eyes Open ◽  
Postural Performance

Objective:To examine the triggering causes of inadequate neuromuscular regulation of posture and subjective imbalance in patients with phobic postural vertigo (PPV), a subtype of functional dizziness.Methods:Postural performance was assessed by center-of-pressure displacements and surface EMG of lower-limb muscles (the tibialis anterior and soleus) in 10 patients with PPV and 10 healthy controls under 4 stance conditions: standing with eyes open or closed and with or without an additional cognitive dual task. The level of muscle cocontraction and the characteristics of open- and closed-loop postural control were analyzed.Results:At baseline (i.e., standing with eyes open without dual task), patients exhibited increased muscle cocontractions (p = 0.003), which were further associated with increased open-loop diffusion activity (p = 0.022) and a lowering of the primary feedback threshold for closed-loop control (p = 0.003). However, postural performance of patients improved considerably and normalized to that of healthy controls when performing an additional dual task.Conclusions:PPV is characterized by a dissociation of subjective postural instability and objectively maintained balance capabilities. The dual-task effects on balance in patients with PPV indicate that this dissociation might result from an increased attention to postural adjustments at baseline, which is normally required only during demanding balance situations. This internal focus on balance control promotes an inappropriate neuromuscular regulation of posture, with increased muscle cocontractions, higher short-term body sway, and an oversensitivity to external stimuli. However, if patients are distracted, muscle cocontractions and balance control normalize. Such distraction may therefore be an effective coping strategy for preventing PPV attacks in susceptible patients.

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