真机调试控制台错误信息：path must be a string Error: path must be a string

路径有什么问题，求大佬告知

var savePath = wx.env.USER_DATA_PATH + "/accelerometer.txt"
let fsm = wx.getFileSystemManager()
        fsm.appendFileSync({
          filePath: savePath,
          data: info.name+','+info.age+','+info.gender+','+info.time+','+info.xaxis+','+info.yaxis+','+info.zaxis+'\n',
          encoding:'utf-8'
          })