interaction_cont

interaction_cont - Interaction Control Manipulation...

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Mod. Sim. Dyn. Sys. Interaction Control Neville Hogan page 1 Interaction Control Manipulation requires interaction – object behavior affects control of force and motion Independent control of force and motion is not possible – object behavior relates force and motion • contact a rigid surface: kinematic constraint • move an object: dynamic constraint Accurate control of force or motion requires detailed models of • manipulator dynamics • object dynamics – object dynamics are usually known poorly, often not at all
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Mod. Sim. Dyn. Sys. Interaction Control Neville Hogan page 2 Object Behavior Can object forces be treated as external (exogenous) disturbances? – the usual assumptions don’t apply: • “disturbance” forces depend on manipulator state • forces often aren’t small by any reasonable measure Can forces due to object behavior be treated as modeling uncertainties? – yes (to some extent) but the usual assumptions don’t apply: • command and disturbance frequencies overlap Example: two people shaking hands – how each person moves influences the forces evoked • “disturbance” forces are state-dependent – each may exert comparable forces and move at comparable speeds • command & “disturbance” have comparable magnitude & frequency
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Mod. Sim. Dyn. Sys. Interaction Control Neville Hogan page 3 Alternative: control port behavior Port behavior: – system properties and/or behaviors “seen” at an interaction port Interaction port: – characterized by conjugate variables that define power flow Key point: [] = = = s) (velocitie flows (forces) efforts in power 1 1 t n t n f f e e P L L f e f e t port behavior is unaffected by contact and interaction
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Mod. Sim. Dyn. Sys. Interaction Control Neville Hogan page 4 Impedance & Admittance Impedance and admittance characterize interaction – a dynamic generalization of resistance and conductance Usually introduced for linear systems but generalizes to nonlinear systems – state-determined representation: – this form may be derived from or depicted as a network model () = = = P V F z V F P V z Z F V z Z z m m n t o s , , , , , & ( ) s L s i s e s Z Cs s i s e s Z = = = = ) ( inductor electrical 1 capacitor electrical x f v x Φ = = & (spring) element elastic 1D nonlinear State equations Output equations Constraint on input & output
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Mod. Sim. Dyn. Sys. Interaction Control Neville Hogan page 5 Impedance & Admittance (continued) Admittance is the causal dual of impedance – Admittance: flow out, effort in – Impedance: effort out, flow in Linear system: admittance is the inverse of impedance Nonlinear system: – causal dual is well-defined: – but may not correspond to any impedance • inverse may not exist ( )( ) () Cs s e s i s Y s Z s Y = = = capacitor electrical 1 = = = P V F y V F P F y Y V F y Y y m m n t o s , , , , , & p v f p Ψ = = & (mass) element inertial 1D nonlinear
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Mod. Sim. Dyn. Sys.
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This note was uploaded on 02/27/2012 for the course MECHANICAL 2.141 taught by Professor Nevillehogan during the Fall '06 term at MIT.

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interaction_cont - Interaction Control Manipulation...

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