OK,I Find a method to deal with this problem.
fisrt convert Ivalue to tuple
and get element can deal with this problem.
auto tpl = output.toTuple();
auto arm_loc = tpl->elements()[0].toTensor();
auto arm_conf = tpl->elements()[1].toTensor();
auto odm_loc = tpl->elements()[2].toTensor();
auto odm_conf = tpl->elements()[3].toTensor();