# CS计算机代考程序代写 Writing Dynamics in State Space Form

Writing Dynamics in State Space Form

Robert Platt Northeastern University

Motivation

In order to reason about complex dynamical systems, we need to write system dynamics in a convenient form.

How encode dynamics of an inverted pendulum? How plan walking trajectories?

How plan flying trajectories?

A simple system

k

b

Force exerted by the spring: Force exerted by the damper:

Force exerted by the inertia of the mass:

m

A simple system

k

b

Consider the motion of the mass

• there are no other forces acting on the mass

• therefore, the equation of motion is the sum of the forces:

m

This is called a linear system. Why?

Let’s express this in ”state space form”:

k

b

A simple system

m

A simple system

Let’s express this in ”state space form”:

k

b

m

A simple system

Let’s express this in ”state space form”:

k

b

m

Let’s express this in ”state space form”:

k

b

A simple system

m

m

Let’s express this in ”state space form”:

k

b

A simple system

A simple system

m

Let’s express this in ”state space form”:

k

b

where

k

b

Suppose that you apply a force:

f

Your finger

A simple system

m

A simple system Suppose that you apply a force:

A simple system Suppose that you apply a force:

Canonical form for a linear system

Continuous time vs discrete time

Continuous time

Discrete time

Continuous time vs discrete time

Continuous time

Discrete time

What are A and B now?

Continuous time vs discrete time

Continuous time

Discrete time

What are A and B now?

Simple system in discrete time We want something in this form:

Simple system in discrete time We want something in this form:

Simple system in discrete time We want something in this form:

Simple system in discrete time We want something in this form:

Continuous time vs discrete time

CT DT

CT

DT

Continuous time vs discrete time

CT DT

CT

DT

In this class, we’re going to focus on discrete time representations…

Think-pair-share External force

Viscous damping

Express DT dynamics of this system in state space form

Think-pair-share

Express DT dynamics of this system in state space form

Think-pair-share

Consider a point robot in the plane with state (x, y). It can make fixed motions dx and dy in either direction. Express this as a linear system of the form: