angularJs select绑定的model取不到值的解决方法

<select ng-model="speed" name="speed" ng-change="vm.h5Video().Playspeed(speed)><option value="1" selected="selected">x1</option> <option value="1.5">x1.5</option> <option value="2">x2</option> <option value="4">x4</option> </select>

$scope.selects = [{id:'1',name:'x1'},{id:'1.5',name:'x1.5'},{id:'2',name:'x2'}];