🚍D.21 Velocity Smoother

nav2_velocity_smoother ဆိုတဲ့ package မှာ lifecycle node တစ်ခုပါတယ်။ သူက Nav2 ကနေ robot controller ဆီပို့တဲ့ velicities တွေကို smooth ဖြစ်အောင်လုပ်ပေးတာ။ ဒီ package သည် Nav2 က လာတဲ့ implement velocity, acceleration, and deadband တို့ကို smoothing ဖြစ်စေဖို့ ရည်ရွယ်ထားတယ်လို့ဆိုပါတယ်။

Params	Description	Type	Default
smoothing_ frequency	Frequency (Hz) to use the last received velocity command to smooth by velocity, acceleration, and deadband constraints. If set approximately to the rate of your local trajectory planner, it should smooth by acceleration constraints velocity commands. If set much higher, it will interpolate and provide a smooth set of commands to the hardware controller	double	20
scale_velocities	Whether or not to adjust other components of velocity proportionally to a component’s required changes due to acceleration limits. This will try to adjust all components to follow the same direction, but still enforces acceleration limits to guarantee compliance, even if it means deviating off commanded trajectory slightly.	bool	FALSE
feedback	Type of feedback to use for the current state of the robot’s velocity. In OPEN_LOOP, it will use the last commanded velocity as the next iteration’s current velocity. When acceleration limits are set appropriately, this is a good assumption. In CLOSED_LOOP, it will use the odometry from the odom topic to estimate the robot’s current speed. In closed loop mode, it is important that the odometry is high rate and low latency, relative to the smoothing frequency.	string	"OPEN_LOOP"
Max_velocity	Maximum velocities (m/s) in [x, y, theta] axes.	vector <double>	[0.5,0.0,2.5]
Min_velocity	Minimum velocities (m/s) in [x, y, theta] axes. This is signed and thus must be negative to reverse. Note: rotational velocities negative direction is a right-hand turn, so this should always be negative regardless of reversing preference.	vector <double>	[-0.5,0.0,-2.5]
deadbond_ velocity	Minimum velocities (m/s) to send to the robot hardware controllers, to prevent small commands from damaging hardware controllers if that speed cannot be achieved due to stall torque.	vecctor <double>	[0.0,0.0,0.0]
vel_timeout	Twist ကို zero တန်ဖိုးနဲ့ publish ပြီး publishing ရပ်ရန် ကြာချိန်။	double	0.0
max_accel	Maximum acceleration to apply to each axis [x, y, theta].	vector <double>	[2.5, 0.0, 3.2]
max+decel	Minimum acceleration to apply to each axis [x, y, theta]. This is signed and thus these should generally all be negative.	vector <double>	[-2.5, 0.0,-3.2]
odom_topic	Topic to find robot odometry, if in CLOSED_LOOP operational mode.	string	"odom"
odom_duration	Time (s) to buffer odometry commands to estimate the robot speed, if in CLOSED_LOOP operational mode.	double	0.1

နမူနာ

velocity_smoother:
  ros__parameters:
    smoothing_frequency: 20.0
    scale_velocities: false
    feedback: "OPEN_LOOP"
    max_velocity: [0.5, 0.0, 2.5]
    min_velocity: [-0.5, 0.0, -2.5]
    deadband_velocity: [0.0, 0.0, 0.0]
    velocity_timeout: 1.0
    max_accel: [2.5, 0.0, 3.2]
    max_decel: [-2.5, 0.0, -3.2]
    odom_topic: "odom"
    odom_duration: 0.1