Некорректное движение объекта

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
 
public class CarControl : BaseControl {
 
    public float speed = 15f;
    public float turnSpeed = 5f;
    public float hoverForce = 65f;
    public float hoverHeight = 3.5f;
    protected float powerInput;
    protected float turnInput;
    protected Rigidbody vehicleRigidbody;
 
    void Awake () {
        vehicleRigidbody = GetComponent <Rigidbody>();
    }
 
    // Use this for initialization
    void Start () {
    
    }
    
    // Update is called once per frame
    void Update () {
    
    }
 
    public void ModeUp() {
        powerInput = 1f;
    }
    
    public void ModeDown() {
        powerInput = -1f;
    }
    
    public void ModeStop() {
        powerInput = 0f;
    }
    
    public void ModeTurnLeft() {
        turnInput = -1f;
    }
    
    public void ModeTurnRight() {
        turnInput = 1f;
    }
    
    public void ModeTurnStop() {
        turnInput = 0f;
    }   
 
    void FixedUpdate() {
        Ray ray = new Ray (transform.position, -transform.up);
        RaycastHit hit;
        
        if (Physics.Raycast(ray, out hit, hoverHeight)) {
            float proportionalHeight = (hoverHeight - hit.distance) / hoverHeight;
            Vector3 appliedHoverForce = Vector3.up * proportionalHeight * hoverForce;
            vehicleRigidbody.AddForce(appliedHoverForce, ForceMode.Acceleration);
        }
        
        vehicleRigidbody.AddRelativeForce(0f, 0f, powerInput * speed);
 
        vehicleRigidbody.AddRelativeTorque(0f, Mathf.Sign() * turnInput * turnSpeed, 0f);
    }
}