Node.js 卡尔曼滤波器 1D

Question

首先，您好，我正在使用 Ibeacon 研究关于内部定位的 node.js javascript。作为我工作的助手：我使用 Evothings Studio。我正在将我的代码传输到 Evothings 工作室并通过我的 android 和 ios 手机查看我的作品。现在我想告诉你我遇到的问题。根据RSSI信号级别，我发现距离在计算中不是很准确。我想用卡尔曼滤波器来清除这个信号电平（RSSI）的噪声。本文介绍了 Javascript 中卡尔曼滤波器的使用。据说很容易实现，但我无法开始练习。 “” 卡尔曼滤波器库：“https://github.com/wouterbulten/kalmanjs”。如何使用此卡尔曼滤波器清除 RSSI 信号中的噪声？如何将卡尔曼滤波器应用于这些代码？

var app = (function()
{
	// Application object.
	var app = {};

	// History of enter/exit events.
	var mRegionEvents = [];

	// Nearest ranged beacon.
	var mNearestBeacon = null;

	// Timer that displays nearby beacons.
	var mNearestBeaconDisplayTimer = null;

	// Background flag.
	var mAppInBackground = false;

	// Background notification id counter.
	var mNotificationId = 0;

	// Mapping of region event state names.
	// These are used in the event display string.
	var mRegionStateNames =
	{
		'CLRegionStateInside': 'Enter',
		'CLRegionStateOutside': 'Exit'
	};

	// Here monitored regions are defined.
	// TODO: Update with uuid/major/minor for your beacons.
	// You can add as many beacons as you want to use.
	var mRegions =
	[
		{
			id: 'BEACON1',
			uuid: 'fda50693-a4e2-4fb1-afcf-c6eb07647825',
			major: 10035,
			minor: 56498
		},
		{
			id: 'region2',
			uuid: 'f7826da6-4fa2-4e98-8024-bc5b71e0893e',
			major: 60378,
			minor: 22122
		}
	];

	// Region data is defined here. Mapping used is from
	// region id to a string. You can adapt this to your
	// own needs, and add other data to be displayed.
	// TODO: Update with major/minor for your own beacons.
	var mRegionData =
	{
		'BEACON1': 'WGX_BEACON1',
		'region2': 'Region Two'
	};

	app.initialize = function()
	{
		document.addEventListener('deviceready', onDeviceReady, false);
		document.addEventListener('pause', onAppToBackground, false);
		document.addEventListener('resume', onAppToForeground, false);
	};

	function onDeviceReady()
	{
		startMonitoringAndRanging();
		startNearestBeaconDisplayTimer();
		displayRegionEvents();
	}

	function onAppToBackground()
	{
		mAppInBackground = true;
		stopNearestBeaconDisplayTimer();
	}

	function onAppToForeground()
	{
		mAppInBackground = false;
		startNearestBeaconDisplayTimer();
		displayRegionEvents();
	}

	function startNearestBeaconDisplayTimer()
	{
		mNearestBeaconDisplayTimer = setInterval(displayNearestBeacon, 1000);
	}

	function stopNearestBeaconDisplayTimer()
	{
		clearInterval(mNearestBeaconDisplayTimer);
		mNearestBeaconDisplayTimer = null;
	}

	function startMonitoringAndRanging()
	{
		function onDidDetermineStateForRegion(result)
		{
			saveRegionEvent(result.state, result.region.identifier);
			displayRecentRegionEvent();
		}

		function onDidRangeBeaconsInRegion(result)
		{
			updateNearestBeacon(result.beacons);
		}

		function onError(errorMessage)
		{
			console.log('Monitoring beacons did fail: ' + errorMessage);
		}

		// Request permission from user to access location info.
		cordova.plugins.locationManager.requestAlwaysAuthorization();

		// Create delegate object that holds beacon callback functions.
		var delegate = new cordova.plugins.locationManager.Delegate();
		cordova.plugins.locationManager.setDelegate(delegate);

		// Set delegate functions.
		delegate.didDetermineStateForRegion = onDidDetermineStateForRegion;
		delegate.didRangeBeaconsInRegion = onDidRangeBeaconsInRegion;

		// Start monitoring and ranging beacons.
		startMonitoringAndRangingRegions(mRegions, onError);
	}

	function startMonitoringAndRangingRegions(regions, errorCallback)
	{
		// Start monitoring and ranging regions.
		for (var i in regions)
		{
			startMonitoringAndRangingRegion(regions[i], errorCallback);
		}
	}

	function startMonitoringAndRangingRegion(region, errorCallback)
	{
		// Create a region object.
		var beaconRegion = new cordova.plugins.locationManager.BeaconRegion(
			region.id,
			region.uuid,
			region.major,
			region.minor);

		// Start ranging.
		cordova.plugins.locationManager.startRangingBeaconsInRegion(beaconRegion)
			.fail(errorCallback)
			.done();

		// Start monitoring.
		cordova.plugins.locationManager.startMonitoringForRegion(beaconRegion)
			.fail(errorCallback)
			.done();
	}

	function saveRegionEvent(eventType, regionId)
	{
		// Save event.
		mRegionEvents.push(
		{
			type: eventType,
			time: getTimeNow(),
			regionId: regionId
		});

		// Truncate if more than ten entries.
		if (mRegionEvents.length > 10)
		{
			mRegionEvents.shift();
		}
	}

	function getBeaconId(beacon)
	{
		return beacon.uuid + ':' + beacon.major + ':' + beacon.minor;
	}

	function isSameBeacon(beacon1, beacon2)
	{
		return getBeaconId(beacon1) == getBeaconId(beacon2);
	}

	function isNearerThan(beacon1, beacon2)
	{
		return beacon1.accuracy > 0
			&& beacon2.accuracy > 0
			&& beacon1.accuracy < beacon2.accuracy;
	}

	function updateNearestBeacon(beacons)
	{
		for (var i = 0; i < beacons.length; ++i)
		{
			var beacon = beacons[i];
			if (!mNearestBeacon)
			{
				mNearestBeacon = beacon;
			}
			else
			{
				if (isSameBeacon(beacon, mNearestBeacon) ||
					isNearerThan(beacon, mNearestBeacon))
				{
					mNearestBeacon = beacon;
				}
			}
		}
	}

	function displayNearestBeacon()
	{
		if (!mNearestBeacon) { return; }

		// Clear element.
		$('#beacon').empty();

		// Update element.
		var element = $(
			'<li>'
			+	'<strong>BEACON1</strong><br />'
			+	'UUID: ' + mNearestBeacon.uuid + '<br />'
			+	'Major: ' + mNearestBeacon.major + '<br />'
			+	'Minor: ' + mNearestBeacon.minor + '<br />'
			+	'Distance: ' + mNearestBeacon.accuracy + '<br />'
			+	'RSSI: ' + mNearestBeacon.rssi + '<br />'
			+ '</li>'
			);
		$('#beacon').append(element);
	}

	function displayRecentRegionEvent()
	{
		if (mAppInBackground)
		{
			// Set notification title.
			var event = mRegionEvents[mRegionEvents.length - 1];
			if (!event) { return; }
			var title = getEventDisplayString(event);

			// Create notification.
			cordova.plugins.notification.local.schedule({
    			id: ++mNotificationId,
    			title: title });
		}
		else
		{
			displayRegionEvents();
		}
	}

	function displayRegionEvents()
	{
		// Clear list.
		$('#events').empty();

		// Update list.
		for (var i = mRegionEvents.length - 1; i >= 0; --i)
		{
			var event = mRegionEvents[i];
			var title = getEventDisplayString(event);
			var element = $(
				'<li>'
				+ '<strong>' + title + '</strong>'
				+ '</li>'
				);
			$('#events').append(element);
		}

		// If the list is empty display a help text.
		if (mRegionEvents.length <= 0)
		{
			var element = $(
				'<li>'
				+ '<strong>'
				+	'İbeacon Taramasi Yapiliyor.'
				+ '</strong>'
				+ '</li>'
				);
			$('#events').append(element);
		}
	}

	function getEventDisplayString(event)
	{
		return event.time + ': '
			+ mRegionStateNames[event.type] + ' '
			+ mRegionData[event.regionId];
	}

	function getTimeNow()
	{
		function pad(n)
		{
			return (n < 10) ? '0' + n : n;
		}

		function format(h, m, s)
		{
			return pad(h) + ':' + pad(m)  + ':' + pad(s);
		}

		var d = new Date();
		return format(d.getHours(), d.getMinutes(), d.getSeconds());
	}

	return app;

})();

app.initialize();

Answer 1

在您完成对卡尔曼滤波器的试验后，您可能会发现距离估计中的误差仍然太高。这是因为除了 RSSI 测量中的随机噪声之外的其他误差源，其中许多可能是影响接收器测量的无线电信号电平的其他变量（例如反射、障碍、天线方向图变化）的函数。

一般来说，使用基于 RSSI 的直接距离计算，在 1 米的真实距离处最多可以准确估计 0.5-2 米，而在更远的距离处准确度要低得多。即使在使用卡尔曼滤波器或运行平均值滤除噪声后也是如此。 （请注意，iOS 距离估计使用 20 秒的 RSSI 运行平均值，而 CLBeacon 上的 RSSI 字段值是 1 秒内的平均值。）

如果使用三边测量或类似的方法来计算位置，你会发现你只能在不超过 1-2 米的非常短的距离内得到可行的结果。