NullReferenceExceptionのエラー

NullReferenceException: Object reference not set to an instance of an object
Done_PlayerController.FixedUpdate () (at Assets/Done/Done_Scripts/Done_PlayerController.cs:61)
とエラーが出ました。

Done_PlayerControllerには

using UnityEngine;
using System.Collections;

[System.Serializable]
public class Done_Boundary 
{
    public float xMin, xMax, zMin, zMax;
}

public class Done_PlayerController : MonoBehaviour
{
    public float speed;
    public float tilt;
    public Done_Boundary boundary;

    public GameObject shot;
    public Transform shotSpawn;
    public float fireRate;
    public SimpleTouchPad touchPad;

    public Boundary[] TouchPad = new Boundary[1];

    private float nextFire;
    private Quaternion calibrationQuaternion;

    void Start(){
        CalibrateAccelerometer ();
    }

    void Update ()
    {
        if (Input.GetButton("Fire1") && Time.time > nextFire) 
        {
            nextFire = Time.time + fireRate;
            Instantiate(shot, shotSpawn.position, shotSpawn.rotation);
            GetComponent<AudioSource>().Play ();
        }
    }

    void CalibrateAccelerometer () {
        Vector3 accelerationSnapshot = Input.acceleration;
        Quaternion rotateQuaternion = Quaternion.FromToRotation (new Vector3 (0.0f, 0.0f, -1.0f), accelerationSnapshot);
        calibrationQuaternion = Quaternion.Inverse (rotateQuaternion);
    }

    Vector3 FixAcceleration (Vector3 acceleration) {
        Vector3 fixedAcceleration = calibrationQuaternion * acceleration;
        return fixedAcceleration;
    }

    void FixedUpdate ()
    {
//        float moveHorizontal = Input.GetAxis ("Horizontal");
//        float moveVertical = Input.GetAxis ("Vertical");
//
//        Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
//        Vector3 accelerationRaw = Input.acceleration;
//        Vector3 acceleration = FixAcceleration (accelerationRaw);

//        Vector3 movement = new Vector3 (acceleration.x, 0.0f, acceleration.y);
        Vector2 direction = touchPad.GetDirection();
        Vector3 movement = new Vector3 (direction.x, 0.0f, direction.y);


        GetComponent<Rigidbody>().velocity = movement * speed;

        GetComponent<Rigidbody>().position = new Vector3
        (
            Mathf.Clamp (GetComponent<Rigidbody>().position.x, boundary.xMin, boundary.xMax), 
            0.0f, 
            Mathf.Clamp (GetComponent<Rigidbody>().position.z, boundary.zMin, boundary.zMax)
        );

        GetComponent<Rigidbody>().rotation = Quaternion.Euler (0.0f, 0.0f, GetComponent<Rigidbody>().velocity.x * -tilt);
    }
}

と書いていて、

Vector2 direction = touchPad.GetDirection();

の部分がおかしいと指摘されました。
インスタンスを作ってください、と言われているのでしょうか？
私はどう記述するべきなのでしょうか？