> For the complete documentation index, see [llms.txt](https://yams.yassrobotics.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://yams.yassrobotics.com/api-reference/c++-reference/mechanisms/flywheel.md).

# FlyWheel

Namespace: `yams::mechanisms::velocity`\
Header: `<yams/mechanisms/velocity/FlyWheel.h>`\
Inherits: `SmartVelocityMechanism`

**Java equivalent:** [Java FlyWheel](/api-reference/java-reference/mechanisms/flywheel.md)

Controls a flywheel or other continuously spinning mechanism. Setpoint is angular velocity or wheel surface speed. Position tracking is not used.

***

## Constructor

```cpp
FlyWheel(config::FlyWheelConfig* config, motorcontrollers::SmartMotorController* smc)
```

Both parameters are non-owning pointers. The `FlyWheelConfig` and `SmartMotorController` must outlive the `FlyWheel` instance.

***

## State Queries

| Method        | Signature                                         | Description              |
| ------------- | ------------------------------------------------- | ------------------------ |
| `GetVelocity` | `units::degrees_per_second_t GetVelocity() const` | Current angular velocity |

***

## Command Factories

| Method                     | Signature                                                                                                                              | Description                                                            |
| -------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------- |
| `Run` (angular)            | `frc2::CommandPtr Run(units::degrees_per_second_t velocity)`                                                                           | Runs indefinitely at `velocity`                                        |
| `Run` (angular supplier)   | `frc2::CommandPtr Run(std::function<units::degrees_per_second_t()> velocity)`                                                          | Supplier variant, re-evaluated each iteration                          |
| `Run` (linear)             | `frc2::CommandPtr Run(units::meters_per_second_t surfaceSpeed)`                                                                        | Controls by wheel surface speed                                        |
| `Run` (linear supplier)    | `frc2::CommandPtr Run(std::function<units::meters_per_second_t()> surfaceSpeed)`                                                       | Supplier variant                                                       |
| `RunTo` (angular)          | `frc2::CommandPtr RunTo(units::degrees_per_second_t velocity, units::degrees_per_second_t tolerance = 5.0_deg_per_s)`                  | Runs until within `tolerance` of `velocity`. Default tolerance: 5°/s.  |
| `RunTo` (angular supplier) | `frc2::CommandPtr RunTo(std::function<units::degrees_per_second_t()> velocity, units::degrees_per_second_t tolerance = 5.0_deg_per_s)` | Supplier variant                                                       |
| `RunTo` (linear)           | `frc2::CommandPtr RunTo(units::meters_per_second_t velocity, units::meters_per_second_t tolerance)`                                    | Surface speed variant; `tolerance` has no default and must be supplied |

{% hint style="info" %}
The C++ `FlyWheel` accepts both angular (`degrees_per_second_t`) and linear surface speed (`meters_per_second_t`) overloads. The linear overload requires `FlyWheelConfig::WithDiameter()` to compute the radius for conversion.
{% endhint %}

***

## Triggers

| Method    | Signature                                                                                                              | Description                                              |
| --------- | ---------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------- |
| `IsNear`  | `frc2::Trigger IsNear(units::degrees_per_second_t velocity, units::degrees_per_second_t within = 5.0_deg_per_s) const` | True when current speed is within `within` of `velocity` |
| `Gte`     | `frc2::Trigger Gte(units::degrees_per_second_t velocity)`                                                              | True when speed ≥ threshold                              |
| `Lte`     | `frc2::Trigger Lte(units::degrees_per_second_t velocity)`                                                              | True when speed ≤ threshold                              |
| `Between` | `frc2::Trigger Between(units::degrees_per_second_t start, units::degrees_per_second_t end)`                            | True when speed is in `[start, end]`                     |

***

## Other Public Methods

| Method                         | Signature                                                 | Description                                                  |
| ------------------------------ | --------------------------------------------------------- | ------------------------------------------------------------ |
| `SetVelocity`                  | `void SetVelocity(units::degrees_per_second_t velocity)`  | Direct setpoint without command wrapper                      |
| `SetSurfaceSpeed`              | `void SetSurfaceSpeed(units::meters_per_second_t speed)`  | Surface speed setpoint; requires `WithDiameter()` in config  |
| `GetRelativeMechanismPosition` | `frc::Translation3d GetRelativeMechanismPosition() const` | 3D position of the mechanism                                 |
| `GetConfig`                    | `const config::FlyWheelConfig& GetConfig() const`         | Returns the configuration this flywheel was constructed with |
| `GetMotor`                     | `motorcontrollers::SmartMotorController* GetMotor()`      | Returns the underlying motor controller pointer              |
| `SimIterate`                   | `void SimIterate() override`                              | Advances flywheel physics simulation one loop iteration      |
| `UpdateTelemetry`              | `void UpdateTelemetry() override`                         | Publishes current state to NetworkTables                     |
| `GetName`                      | `std::string GetName() const override`                    | Returns the mechanism name                                   |

***

## Example

```cpp
config::FlyWheelConfig flywheelConfig;
flywheelConfig.WithDiameter(0.1_m)        // required for surface speed overloads
              .WithTelemetryName("Shooter");

motorcontrollers::SmartMotorControllerConfig motorConfig;
motorConfig.WithMotorInverted(false)
           .WithMotorGearing(gearing::MechanismGearing{1.0})
           .WithFeedback(0.0, 0.0002, 0.0);

// motor is a SmartMotorController* created elsewhere
velocity::FlyWheel flywheel{&flywheelConfig, motor};

// Run at a fixed angular velocity:
frc2::CommandPtr spinUp = flywheel.RunTo(3600_deg_per_s, 50_deg_per_s);

// Or by surface speed (requires WithDiameter in config):
frc2::CommandPtr spinUpLinear = flywheel.RunTo(15_mps, 0.3_mps);
```

{% @github-files/github-code-block url="<https://github.com/Yet-Another-Software-Suite/YAMS/blob/master/examples/cpptest/src/main/cpp/subsystems/ShooterSubsystem.cpp#L43-L50>" %}

***

## See Also

* [Java FlyWheel](/api-reference/java-reference/mechanisms/flywheel.md)
* [C++ FlyWheelConfig](/api-reference/c++-reference/config/flywheel-config.md)