diff --git a/source/Behavior/BoundaryConstraint.ts b/source/Behavior/BoundaryConstraint.ts
index d047173..d77b3d5 100644
--- a/source/Behavior/BoundaryConstraint.ts
+++ b/source/Behavior/BoundaryConstraint.ts
@@ -57,7 +57,6 @@ class BoundaryConstraint extends Behavior<IBoundaryConstraintBehaviorParameter,
 				}
 
 			} else {
-
 				fx = 0;
 				fy = 0;
 				fz = 0;
@@ -65,11 +64,13 @@ class BoundaryConstraint extends Behavior<IBoundaryConstraintBehaviorParameter,
 			}
 		}
 
-		individual.applyForce(
-			fx * this.parameter.strength,
-			fy * this.parameter.strength,
-			fz * this.parameter.strength
-		);
+        if (fLen && fLen !== Infinity) {
+            individual.applyForce(
+                fx * this.parameter.strength / fLen,
+                fy * this.parameter.strength / fLen,
+                fz * this.parameter.strength / fLen
+            );
+        }
     }
 
 	public override terms: Record<string, Record<string, string>> = {
diff --git a/source/Behavior/Tracking.ts b/source/Behavior/Tracking.ts
index d1e457e..0c6bc22 100644
--- a/source/Behavior/Tracking.ts
+++ b/source/Behavior/Tracking.ts
@@ -5,7 +5,9 @@ import { Model } from "@Model/Model";
 
 type ITrackingBehaviorParameter = {
     target: "LG",
-	strength: "number"
+	strength: "number",
+    range: "number",
+    lock: "boolean"
 }
 
 type ITrackingBehaviorEvent = {}
@@ -24,12 +26,15 @@ class Tracking extends Behavior<ITrackingBehaviorParameter, ITrackingBehaviorEve
 
 	public override parameterOption = {
 		target: { type: "CLG", name: "$Target" },
-		strength: { type: "number", name: "$Strength", defaultValue: 10, numberMin: 0, numberStep: .1 }
+        lock: { type: "boolean", name: "$Lock", defaultValue: false },
+        range: { type: "number", name: "$Range", defaultValue: 4, numberMin: 0, numberStep: .1 },
+		strength: { type: "number", name: "$Strength", defaultValue: 1, numberMin: 0, numberStep: .1 }
 	};
 
-    public effect = (individual: Individual, group: Group, model: Model, t: number): void => {
-		let target: Individual | undefined;
-		let currentDistant: number = Infinity;
+    private target: Individual | undefined = undefined;
+    private currentDistant: number = Infinity;
+
+    private searchTarget(individual: Individual) {
 
 		for (let i = 0; i < this.parameter.target.objects.length; i++) {
 			const targetGroup = this.parameter.target.objects[i];
@@ -40,19 +45,79 @@ class Tracking extends Behavior<ITrackingBehaviorParameter, ITrackingBehaviorEve
 				if (targetIndividual === individual) return;
 				let dis = targetIndividual.distanceTo(individual);
 
-				if (dis < currentDistant) {
-					target = targetIndividual;
-					currentDistant = dis;
+				if (dis < this.currentDistant && dis <= this.parameter.range) {
+					this.target = targetIndividual;
+					this.currentDistant = dis;
 				}
 
 			});
 		}
+    }
 
-		if (target) {
+    private clearTarget() {
+        this.target = undefined as Individual | undefined;
+        this.currentDistant = Infinity;
+    }
+
+    public effect = (individual: Individual, group: Group, model: Model, t: number): void => {
+
+        this.clearTarget();
+
+        if (this.parameter.lock) {
+
+            let isValidTarget = false;
+            this.target = individual.getData("Tracking.lock.target");
+
+            if (this.target) {
+
+                // 校验目标所在的群是否仍是目标
+                let isInTarget = false;
+                for (let i = 0; i < this.parameter.target.objects.length; i++) {
+                    if (this.parameter.target.objects[i].equal(this.target.group)) {
+                        isInTarget = true;
+                        break;
+                    }
+                }
+
+                // 如果还在目标范围内，校验距离
+                if (isInTarget) {
+                    let dis = individual.distanceTo(this.target);
+
+                    // 校验成功
+                    if (dis <= this.parameter.range) {
+                        this.currentDistant = dis;
+                        isValidTarget = true;
+                    }
+                }
+            }
+
+            // 如果目标无效，尝试搜索新的目标
+            if (!isValidTarget) {
+
+                this.clearTarget();
+                this.searchTarget(individual);
+
+                // 如果成功搜索，缓存目标
+                if (this.target && this.currentDistant && this.currentDistant !== Infinity) {
+                    individual.setData("Tracking.lock.target", this.target);
+                }
+
+                // 搜索失败，清除目标
+                else {
+                    individual.setData("Tracking.lock.target", undefined);
+                }
+            }
+        }
+
+        else {
+            this.searchTarget(individual);
+        }
+
+		if (this.target && this.currentDistant && this.currentDistant !== Infinity) {
 			individual.applyForce(
-				(target.position[0] - individual.position[0]) * this.parameter.strength,
-				(target.position[1] - individual.position[1]) * this.parameter.strength,
-				(target.position[2] - individual.position[2]) * this.parameter.strength
+				(this.target.position[0] - individual.position[0]) * this.parameter.strength / this.currentDistant,
+				(this.target.position[1] - individual.position[1]) * this.parameter.strength / this.currentDistant,
+				(this.target.position[2] - individual.position[2]) * this.parameter.strength / this.currentDistant
 			);
 		}
     }
@@ -66,6 +131,14 @@ class Tracking extends Behavior<ITrackingBehaviorParameter, ITrackingBehaviorEve
 			"ZH_CN": "追踪目标",
 			"EN_US": "Tracking target"
 		},
+        "$Lock": {
+            "ZH_CN": "追踪锁定",
+			"EN_US": "Tracking lock"
+        },
+        "$Range": {
+            "ZH_CN": "追踪范围",
+			"EN_US": "Tracking range"
+        },
 		"$Strength": {
 			"ZH_CN": "追踪强度系数",
 			"EN_US": "Tracking intensity coefficient"
diff --git a/source/Model/CtrlObject.ts b/source/Model/CtrlObject.ts
index 3dca039..19a768f 100644
--- a/source/Model/CtrlObject.ts
+++ b/source/Model/CtrlObject.ts
@@ -61,8 +61,8 @@ class CtrlObject extends LabelObject {
     /**
      * 判断是否为相同对象
      */
-    public equal(obj: CtrlObject): boolean {
-        return this === obj || this.id === obj.id;
+    public equal(obj?: CtrlObject): boolean {
+        return this === obj || this.id === obj?.id;
     }
 
     /**
diff --git a/source/Model/Group.ts b/source/Model/Group.ts
index d28b7f1..597adca 100644
--- a/source/Model/Group.ts
+++ b/source/Model/Group.ts
@@ -272,9 +272,11 @@ class Group extends CtrlObject {
     public remove(individual: Individual[] | Individual): this {
         if (Array.isArray(individual)) {
             for (let i = 0; i < individual.length; i++) {
+                individual[i].group = undefined;
                 this.individuals.delete(individual[i]);
             }
         } else {
+            individual.group = undefined;
             this.individuals.delete(individual);
         }
         return this;
diff --git a/source/Model/Individual.ts b/source/Model/Individual.ts
index 2685dfa..ba41bb9 100644
--- a/source/Model/Individual.ts
+++ b/source/Model/Individual.ts
@@ -88,7 +88,7 @@ class Individual {
 	/**
 	 * 所属群组
 	 */
-	public group: Group;
+	public group: Group | undefined;
 
 	/**
 	 * 初始化
@@ -97,11 +97,16 @@ class Individual {
 		this.group = group;
 	}
 
+    public isDie(): boolean {
+        return !!this.group;
+    }
+
     /**
      * 死亡
      */
     public die(): this {
-        this.group.remove(this);
+        this.group?.remove(this);
+        this.group = undefined;
         return this;
     }
 
@@ -110,7 +115,7 @@ class Individual {
      * @param newGroup 新群体
      */
     public transfer(newGroup: Group): this {
-        this.group.remove(this);
+        this.group?.remove(this);
         newGroup.add(this);
         this.group = newGroup;
         return this;