用box2dweb 做一个旋转刚体，用马达怎么实现？

Creator 2.x
#1

创建连接代码如下：这个代码不圆形刚体什么不动

private createRevoluteJoint(body, thing:IThing):void{
if (thing && thing.is_rotation && body) {
let center = body.GetWorldCenter();
var pointDef = new this.b2BodyDef;
pointDef.type = this.Box2D.b2BodyType.b2_staticBody;
pointDef.position.Set(center.x, center.y);
let point = this.world.CreateBody(pointDef);
let fixDef = new this.b2FixtureDef;
fixDef.density = 1000;
fixDef.friction = 0;
fixDef.restitution = 0;

            let shape = new this.b2CircleShape;
            shape.Set(new this.b2Vec2(0, 0), 2);
            fixDef.shape = shape;
            point.CreateFixture(fixDef);
            let jointDef = new this.b2RevoluteJointDef;
            jointDef.Initialize(point, body, center);
            jointDef.collideConnected = true;
            jointDef.enableMotor = true;
            jointDef.motorSpeed = 1;
            jointDef.maxMotorTorque = 100;
            this.world.CreateJoint(jointDef);
            body.SetAngularVelocity(thing.angle_speed * Math.PI / 180);
        }
    }

想创建一个圆形刚体在某个位置自己转动，用马达怎么做？自己不断的提供动力转动？
谢谢