Class DoubleSpringSim

Simulation of two blocks connected by springs. Movement is only along one dimension. No gravity force or damping force. The configuration is:

wall1-spring1-block1-spring2-block2-spring3-wall2

Variables and Parameters

Variables:

vars[0] = u1 = position of block 1
vars[1] = u2 = position of block 2
vars[2] = v1 = velocity of block 1
vars[3] = v2 = velocity of block 2

Parameters:

R = rest length of spring
k = spring constant
b = damping
m = mass
L = spring stretch
F = force

Equations of Motion

Forces:

F1 = -k1 L1 + k2 L2 - b v1 = m1 v1'
F2 = -k2 L2 + k3 L3 - b v2 = m2 v2'

Equations of Motion:

u1' = v1
u2' = v2
v1' = F1/m1 = (-k1 L1 + k2 L2 - b v1) / m1
v2' = F2/m2 = (-k2 L2 + k3 L3 - b v2) / m2

TO DO make a vertical configuration with gravity

Hierarchy (view full)

AbstractODESim
- DoubleSpringSim

Implements

Constructors

constructor

new DoubleSpringSim(thirdSpring, opt_name?): DoubleSpringSim
Parameters
- thirdSpring: boolean
  whether to have the third spring
- Optional opt_name: string
  name of this as a Subject
Returns DoubleSpringSim
Overrides AbstractODESim.constructor
- Defined in sims/springs/DoubleSpringSim.ts:107

Properties

`Private` dragBlock_

dragBlock_: number = -1

the block being dragged, or -1 when no drag is happening

`Protected` initialState_

initialState_: null | number[] = null

Initial values.

Methods

addObserver

addObserver(observer): void
Adds the given Observer to this Subject's list of Observers, so that the Observer will be notified of changes in this Subject. An Observer may call Subject.addObserver during its observe method.
Parameters
- observer: Observer
  the Observer to add
Returns void
Implementation of ODESim.addObserver
Inherited from AbstractODESim.addObserver
- Defined in lab/util/AbstractSubject.ts:67

addParameter

addParameter(parameter): void
Adds the Parameter to the list of this Subject's available Parameters.
Parameters
- parameter: Parameter
  the Parameter to add
Returns void
Throws
if a Parameter with the same name already exists.
Inherited from AbstractODESim.addParameter
- Defined in lab/util/AbstractSubject.ts:100

broadcast

broadcast(evt): void
Notifies all Observers that this Subject has changed by calling observe on each Observer.

An Observer may call addObserver or removeObserver during its observe method.
Parameters
- evt: SubjectEvent
  a SubjectEvent with information relating to the change
Returns void
Implementation of ODESim.broadcast
Inherited from AbstractODESim.broadcast
- Defined in lab/util/AbstractSubject.ts:110

broadcastParameter

broadcastParameter(name): void
Notifies all Observers that the Parameter with the given name has changed by calling observe on each Observer.
Parameters
- name: string
  the language-independent or English name of the Parameter that has changed
Returns void
Throws
if there is no Parameter with the given name
Implementation of ODESim.broadcastParameter
Inherited from AbstractODESim.broadcastParameter
- Defined in lab/util/AbstractSubject.ts:132

evaluate

evaluate(vars, change, _timeStep): null | object
Defines the differential equations of this ODESim; for an input set of variables, returns the current rate of change for each variable (the first derivative of each variable with respect to time).

The timeStep is the time since the state variables were last fully calculated, which can be and often is zero. The current time can be regarded as getTime() + timeStep. The input variables correspond to the Simulation state at that time. Note that timeStep is different from the time step used to advance the Simulation (as in AdvanceStrategy.advance). The timeStep is typically used when finding collisions in CollisionSim.findCollisions.
Parameters
- vars: number[]
  the current array of state variables (input), corresponding to the state at getTime() + timeStep
- change: number[]
  array of change rates for each variable (output), all values are zero on entry.
- _timeStep: number
  the current time step (might be zero)
Returns null | object
null if the evaluation succeeds, otherwise an object relating to the error that occurred. The change array contains the output results.
Implementation of ODESim.evaluate
Overrides AbstractODESim.evaluate
- Defined in sims/springs/DoubleSpringSim.ts:369

finishDrag

finishDrag(_simObject, _location, _offset): void
Called at the end of a mouse drag operation, performs whatever action is appropriate. Only called if startDrag returned true.
Parameters
- _simObject: null | SimObject
  the SimObject being dragged, or null if no SimObject was found
- _location: Vector
  the location of the mouse in simulation coordinates of the SimView where simObject was found, or in the focus view if simObject is null.
- _offset: Vector
  distance from the initial object position to the mouse location at start of drag.
Returns void
Implementation of EventHandler.finishDrag
- Defined in sims/springs/DoubleSpringSim.ts:360

`Protected` getBroadcast

getBroadcast(): boolean
Returns whether broadcasting is enabled for this Subject. See setBroadcast.

Returns boolean
whether broadcasting is enabled for this Subject
Inherited from AbstractODESim.getBroadcast
- Defined in lab/util/AbstractSubject.ts:144

getClassName

getClassName(): string
Returns name of class of this object.

Returns string
name of class of this object.
Overrides AbstractODESim.getClassName
- Defined in sims/springs/DoubleSpringSim.ts:206

getDamping

getDamping(): number
Returns number
- Defined in sims/springs/DoubleSpringSim.ts:515

getEnergyInfo

getEnergyInfo(): EnergyInfo
Returns the current EnergyInfo for this system.

Returns EnergyInfo
an EnergyInfo object representing the current energy of this system.
Implementation of EnergySystem.getEnergyInfo
- Defined in sims/springs/DoubleSpringSim.ts:274

getLength

getLength(): number
Return spring resting length

Returns number
spring resting length
- Defined in sims/springs/DoubleSpringSim.ts:469

getMass1

getMass1(): number
Return mass of pendulum block 1.

Returns number
mass of pendulum block 1
- Defined in sims/springs/DoubleSpringSim.ts:431

getMass2

getMass2(): number
Return mass of pendulum block 2.

Returns number
mass of pendulum block 2
- Defined in sims/springs/DoubleSpringSim.ts:450

getName

getName(): string
Return the language-independent name of this Subject for scripting purposes.

Returns string
name the language-independent name of this Subject
Implementation of ODESim.getName
Inherited from AbstractODESim.getName
- Defined in lab/util/AbstractSubject.ts:154

getObservers

getObservers(): Observer[]
Returns a copy of the list of Observers of this Subject.

Returns Observer[]
a copy of the list of Observers of this Subject.
Implementation of ODESim.getObservers
Inherited from AbstractODESim.getObservers
- Defined in lab/util/AbstractSubject.ts:159

getPEOffset

getPEOffset(): number
Returns the potential energy offset.

Returns number
the potential energy offset
Implementation of EnergySystem.getPEOffset
- Defined in sims/springs/DoubleSpringSim.ts:282

getParameter

getParameter(name): Parameter
Returns the Parameter with the given name.
Parameters
- name: string
  the language-independent or English name of the Parameter
Returns Parameter
the Parameter with the given name

Throws
if there is no Parameter with the given name
Implementation of ODESim.getParameter
Inherited from AbstractODESim.getParameter
- Defined in lab/util/AbstractSubject.ts:173

getParameterBoolean

getParameterBoolean(name): ParameterBoolean
Returns the ParameterBoolean with the given name.
Parameters
- name: string
  the language-independent or English name of the ParameterBoolean
Returns ParameterBoolean
the ParameterBoolean with the given name

Throws
if there is no ParameterBoolean with the given name
Implementation of ODESim.getParameterBoolean
Inherited from AbstractODESim.getParameterBoolean
- Defined in lab/util/AbstractSubject.ts:182

getParameterNumber

getParameterNumber(name): ParameterNumber
Returns the ParameterNumber with the given name.
Parameters
- name: string
  the language-independent or English name of the ParameterNumber
Returns ParameterNumber
the ParameterNumber with the given name

Throws
if there is no ParameterNumber with the given name
Implementation of ODESim.getParameterNumber
Inherited from AbstractODESim.getParameterNumber
- Defined in lab/util/AbstractSubject.ts:191

getParameterString

getParameterString(name): ParameterString
Returns the ParameterString with the given name.
Parameters
- name: string
  the language-independent or English name of the ParameterString
Returns ParameterString
the ParameterString with the given name

Throws
if there is no ParameterString with the given name
Implementation of ODESim.getParameterString
Inherited from AbstractODESim.getParameterString
- Defined in lab/util/AbstractSubject.ts:200

getParameters

getParameters(): Parameter[]
Returns a copy of the list of this Subject's available Parameters.

Returns Parameter[]
a copy of the list of available Parameters for this Subject
Implementation of ODESim.getParameters
Inherited from AbstractODESim.getParameters
- Defined in lab/util/AbstractSubject.ts:209

getSimList

getSimList(): SimList
Returns the list of SimObject's that represent this Simulation.

Returns SimList
the list of SimObjects that represent this simulation
Implementation of ODESim.getSimList
Inherited from AbstractODESim.getSimList
- Defined in lab/model/ODESim.ts:165

getStiffness

getStiffness(): number
Returns spring stiffness

Returns number
spring stiffness
- Defined in sims/springs/DoubleSpringSim.ts:490

getThirdSpring

getThirdSpring(): boolean
Return whether to have the third spring

Returns boolean
whether to have the third spring
- Defined in sims/springs/DoubleSpringSim.ts:409

getTime

getTime(): number
Returns the current Simulation time.

Returns number
the current Simulation time.

Throws
if there is no time variable for the simulation
Implementation of ODESim.getTime
Inherited from AbstractODESim.getTime
- Defined in lab/model/ODESim.ts:124

getVarsList

getVarsList(): VarsList
Returns the VarsList that represents the current state of this Simulation.

Returns VarsList
the VarsList that represents the current state of this Simulation
Implementation of ODESim.getVarsList
Inherited from AbstractODESim.getVarsList
- Defined in lab/model/ODESim.ts:129

handleKeyEvent

handleKeyEvent(_evt, _pressed, _modifiers): void
Called when a key is pressed or released, performs whatever action is appropriate for that event.
Parameters
- _evt: KeyboardEvent
  the KeyboardEvent that happened
- _pressed: boolean
  true means this is a key-down event; false means a key-up event
- _modifiers: ModifierKeys
  the modifier keys down during event
Returns void
Implementation of EventHandler.handleKeyEvent
- Defined in sims/springs/DoubleSpringSim.ts:365

modifyObjects

modifyObjects(): void
Updates the SimObjects to match the current internal state of the Simulation.

Returns void
Implementation of ODESim.modifyObjects
Overrides AbstractODESim.modifyObjects
- Defined in sims/springs/DoubleSpringSim.ts:297

mouseDrag

mouseDrag(simObject, location, offset): void
Called at each movement during a mouse drag, performs whatever action is appropriate. Only called if startDrag returned true. The SimObject being moved is passed in, along with the current mouse position, in simulation coordinates, and an offset calculated at the start of the drag.

Setting the SimObject position to (x - offsetX, y - offsetY) will move the SimObject smoothly along with the mouse movement.
Parameters
- simObject: null | SimObject
  the SimObject being dragged, or null if no SimObject was found
- location: Vector
  the location of the mouse in simulation coordinates of the SimView where simObject was found, or in the focus view if simObject is null.
- offset: Vector
  distance from the initial object position (from DisplayObject.getPosition) to the mouse location at start of drag.
Returns void
Implementation of EventHandler.mouseDrag
- Defined in sims/springs/DoubleSpringSim.ts:341

`Private` moveObjects

moveObjects(vars): void
Parameters
- vars: number[]
Returns void
- Defined in sims/springs/DoubleSpringSim.ts:317

removeObserver

removeObserver(observer): void
Removes the Observer from this Subject's list of Observers. An Observer may call removeObserver during its observe method.
Parameters
- observer: Observer
  the Observer to detach from list of Observers
Returns void
Implementation of ODESim.removeObserver
Inherited from AbstractODESim.removeObserver
- Defined in lab/util/AbstractSubject.ts:214

removeParameter

removeParameter(parameter): void
Removes the Parameter from the list of this Subject's available Parameters.
Parameters
- parameter: Parameter
  the Parameter to remove
Returns void
Inherited from AbstractODESim.removeParameter
- Defined in lab/util/AbstractSubject.ts:226

reset

reset(): void
Sets the Simulation back to its initial conditions, see saveInitialState, and calls modifyObjects. Broadcasts event named 'RESET'.

Returns void
Implementation of ODESim.reset
Inherited from AbstractODESim.reset
- Defined in lab/model/ODESim.ts:137

restState

restState(): void

Sets the simulation to a motionless state.

R = restLength of springs
k = stiffness of springs
L = stretch of springs
u = position of bobs

Need forces on each block to be zero

0 = -k1 L1 + k2 L2
0 = -k2 L2 + k3 L3

Really its an equation for finding u1, u2 = position of the two blocks.

0 = -k1 (u1 - Wall1 - R1) + k2 (u2 - u1 - R2)
0 = -k2 (u2 - u1 - R2) + k3 (Wall2 - u2 - R3)

We have 2 equations in 2 unknowns, solve the first for u2

0 = -k1 (u1 - Wall1 - R1) + k2 (u2 - u1 - R2)
0 = -(k1/k2) (u1 - Wall1 - R1) + u2 - u1 - R2
u2 = (k1/k2)(u1 - Wall1 - R1) + u1 + R2

Plug that into the second equation and solve for u1:

0 = -k2 (u2 - u1 - R2) + k3 (Wall2 - u2 - R3)
0 = -k2 ((k1/k2)(u1 - Wall1 - R1) + u1 + R2 - u1 - R2)
    + k3 (Wall2 - ((k1/k2)(u1 - Wall1 - R1) + u1 + R2) - R3)
0 = -k1 (u1 - Wall1 - R1)
    + k3 (Wall2 - (k1/k2)(u1 - Wall1 - R1) - u1 - R2 - R3)
0 = -k1 u1 + k1 Wall1 + k1 R1
    + k3 Wall2 - (k3 k1/k2)(u1 - Wall1 - R1) - k3 u1 - k3 R2 - k3 R3
0 = -k1 u1 - (k3 k1/k2) u1- k3 u1
    + k1 Wall1 + k1 R1 + k3 Wall2 + (k3 k1/k2)(Wall1 + R1) - k3 R2 - k3 R3
(k1 + (k3 k1/k2) + k3) u1 =
    + k1 Wall1 + k1 R1 + k3 Wall2 + (k3 k1/k2)(Wall1 + R1) - k3 R2 - k3 R3
u1 = (k1 Wall1 + k1 R1 + k3 Wall2 + (k3 k1/k2)(Wall1 + R1) - k3 R2 - k3 R3)
    / (k1 + (k3 k1/k2) + k3)

Returns void

restoreState

restoreState(): void
Restores the Simulation state that was saved with saveState.

Returns void
Implementation of ODESim.restoreState
Inherited from AbstractODESim.restoreState
- Defined in lab/model/ODESim.ts:147

saveInitialState

saveInitialState(): void
Saves the current variables and time as the initial state, so that this initial state can be restored with reset. Broadcasts event named 'INITIAL_STATE_SAVED'.

Returns void
Implementation of ODESim.saveInitialState
Inherited from AbstractODESim.saveInitialState
- Defined in lab/model/ODESim.ts:154

saveState

saveState(): void
Saves the current state of the Simulation, so that we can back up to this state later on. The state is defined mainly by the set of Simulation variables, see getVarsList, but can include other data. This state is typically used for collision detection as the before collision state, see CollisionSim.findCollisions.

Returns void
Implementation of ODESim.saveState
Inherited from AbstractODESim.saveState
- Defined in lab/model/ODESim.ts:160

`Protected` setBroadcast

setBroadcast(value): boolean
Sets whether this Subject will broadcast events, typically used to temporarily disable broadcasting. Intended to be used in situations where a subclass overrides a method that broadcasts an event. This allows the subclass to prevent the superclass broadcasting that event, so that the subclass can broadcast the event when the method is completed.
Parameters
- value: boolean
  whether this Subject should broadcast events
Returns boolean
the previous value
Inherited from AbstractODESim.setBroadcast
- Defined in lab/util/AbstractSubject.ts:238

setDamping

setDamping(value): void
Parameters
- value: number
Returns void
- Defined in sims/springs/DoubleSpringSim.ts:522

setLength

setLength(value): void
Set spring resting length
Parameters
- value: number
  spring resting length
Returns void
- Defined in sims/springs/DoubleSpringSim.ts:476

setMass1

setMass1(value): void
Set mass of pendulum block 1
Parameters
- value: number
  mass of pendulum block 1
Returns void
- Defined in sims/springs/DoubleSpringSim.ts:438

setMass2

setMass2(value): void
Set mass of pendulum block 2
Parameters
- value: number
  mass of pendulum block 2
Returns void
- Defined in sims/springs/DoubleSpringSim.ts:457

setPEOffset

setPEOffset(value): void
Sets the potential energy offset.
Parameters
- value: number
  the potential energy offset
Returns void
Implementation of EnergySystem.setPEOffset
- Defined in sims/springs/DoubleSpringSim.ts:287

setStiffness

setStiffness(value): void
Sets spring stiffness
Parameters
- value: number
  spring stiffness
Returns void
- Defined in sims/springs/DoubleSpringSim.ts:497

setTerminal

setTerminal(terminal): void
Sets the Terminal object that this simulation can print data into.
Parameters
- terminal: null | Terminal
  the Terminal object that this simulation can print data into.
Returns void
Implementation of ODESim.setTerminal
Inherited from AbstractODESim.setTerminal
- Defined in lab/model/ODESim.ts:177

setThirdSpring

setThirdSpring(value): void
Set whether to have the third spring
Parameters
- value: boolean
  whether to have the third spring
Returns void
- Defined in sims/springs/DoubleSpringSim.ts:416

`Protected` setVarsList

setVarsList(varsList): void
Sets the VarsList for this simulation.
Parameters
- varsList: VarsList
  the VarsList to use in this simulation
Returns void
Inherited from AbstractODESim.setVarsList
- Defined in lab/model/ODESim.ts:172

startDrag

startDrag(simObject, _location, _offset, _dragBody, _modifiers): boolean
Called at the start of a mouse drag. The nearest dragable SimObject is passed in, along with mouse position in simulation coordinates. If no dragable SimObject was found, null is passed for the first argument. If the EventHandler does not recognize the SimObject then it should return false.
Parameters
- simObject: null | SimObject
  the SimObject that is nearest to the mouse drag coordinates, or null if no SimObject was found
- _location: Vector
  the location of the mouse in simulation coordinates of the SimView where simObject was found, or in the focus view if simObject is null.
- _offset: Vector
  distance from the initial object position (from DisplayObject.getPosition) to the mouse location at start of drag
- _dragBody: null | Vector
  location of 'drag point' on the SimObject in body coordinates of the SimObject; this is where for example a spring will be attached on the SimObject when dragging; or null when no SimObject was found
- _modifiers: ModifierKeys
  the modifier keys down during event
Returns boolean
true if the EventHandler will handle dragging the SimObject
Implementation of EventHandler.startDrag
- Defined in sims/springs/DoubleSpringSim.ts:327

toString

toString(): string
Returns string
Inherit Doc
Overrides AbstractODESim.toString
- Defined in sims/springs/DoubleSpringSim.ts:193

toStringShort

toStringShort(): string
Returns a minimal string representation of this object, usually giving just identity information like the class name and name of the object.

For an object whose main purpose is to represent another Printable object, it is recommended to include the result of calling toStringShort on that other object. For example, calling toStringShort() on a DisplayShape might return something like this:
```
DisplayShape{polygon:Polygon{'chain3'}}
```
Returns string
a minimal string representation of this object.
Implementation of EnergySystem.toStringShort
Inherited from AbstractODESim.toStringShort
- Defined in lab/util/AbstractSubject.ts:61

Class DoubleSpringSim

Variables and Parameters

Equations of Motion

Hierarchy (view full)

Implements

Index

Constructors

Properties

Methods

Constructors

constructor

Parameters

thirdSpring: boolean

Optional opt_name: string

Returns DoubleSpringSim

Properties

Private dragBlock_

Protected initialState_

Methods

addObserver

Parameters

observer: Observer

Returns void

addParameter

Parameters

parameter: Parameter

Returns void

Throws

broadcast

Parameters

evt: SubjectEvent

Returns void

broadcastParameter

Parameters

name: string

Returns void

Throws

evaluate

Parameters

vars: number[]

change: number[]

_timeStep: number

Returns null | object

finishDrag

Parameters

_simObject: null | SimObject

_location: Vector

_offset: Vector

Returns void

Protected getBroadcast

Returns boolean

getClassName

Returns string

getDamping

Returns number

getEnergyInfo

Returns EnergyInfo

getLength

Returns number

getMass1

Returns number

getMass2

Returns number

getName

Returns string

getObservers

Returns Observer[]

getPEOffset

Returns number

getParameter

Parameters

name: string

Returns Parameter

Throws

getParameterBoolean

Parameters

name: string

Returns ParameterBoolean

Throws

getParameterNumber

`Optional` opt_name: string

`Private` dragBlock_

`Protected` initialState_

`Protected` getBroadcast

`Private` moveObjects

`Protected` setBroadcast